CHEM 101/105 Numbers and mass / Counting and weighing Lect-03

Save this PDF as:
 WORD  PNG  TXT  JPG

Size: px
Start display at page:

Download "CHEM 101/105 Numbers and mass / Counting and weighing Lect-03"

Transcription

1 CHEM 101/105 Numbers and mass / Counting and weighing Lect-03 Interpretation of Elemental Chemical Symbols, Chemical Formulas, and Chemical Equations Interpretation of an element's chemical symbol depends on context and viewpoint. Zirconium (at.no. 40) has the symbol Zr. From a microscopic view, the symbol can represent one atom as an independent entity, and/or the mass of one atom, amu. From a macroscopic view, the symbol can represent one mole of atoms, and/or a mass of grams of zirconium. It depends on context. Interpretation of a chemical formula for a molecular compound is likewise interpreted in several ways. Cholesterol has the formula C 27 H 46 O with a molecular weight of 386. From a microscopic view, the formula can represent one molecule, or the number of atoms in one molecule, or refer to the mass of one molecule, 386 amu. From a macroscopic view the formula can represent one mole of molecules as well as a mass of 386 grams of the compound. A balanced chemical equation depicting a chemical reaction is similarly interpreted in several ways. counting, masses and weighing, are equivalent concepts in chemistry; chemists count by weighing. Numbers and Chemical Stoichiometry refers to the application of number / mass content as represented by symbols of elements, formulas of compounds, and chemical equations depicting reactions, and is used to determine quantitative information about chemical substances and chemical processes. It is an omnipresent part of all chemistry, and in CHEM 101/105 the majority of our work involves stoichiometric calculations. 1. Chemical Stoichiometry given a formula for a compound, find its per cent composition. Per cent is often referred to as "part over whole times 100". If the "part" is the amount of a given element in the compound, then the per cent composition of that element in the compound will be "part over whole, times 100". Consider cholesterol: total mass of a cholesterol molecule = 386 amu (the whole) mass of element carbon in cholesterol = (27 carbon atoms)x(12 amu per carbon) = 324 amu (the part) per cent carbon (by weight) in cholesterol = similarly for the other atom-types present in cholesterol: Of course the sum of all percentages add to 100. [ 324 amu C] [ 386 amu cmpd] % H = 46., % O. = = = 414 = % C (part over whole) A. Calcium (Ca) and chlorine (Cl) combine to form a compound. In one reaction g of Ca combined with g of Cl to form g of compound, with some Cl left over. What is the per cent composition of this compound? B. An oxide of mercury was decomposed by Joseph Priestly in a historically important reaction. After g of the oxide was heated, and all of the oxygen driven off, then g of pure mercury remained. What is the per cent composition of the oxide. Correctly name the oxide. C. Benzoic acid is composed of the elements C, H, and O. When a g sample of benzoic acid is burned (i.e., completely combusted in an XS of oxygen gas) all of the carbon is converted to g of carbon dioxide, and all hydrogen is converted to g of water. What is the per cent composition of benzoic acid? Before continuing it will be worthwhile to pause and reflect upon the true meaning of atomic weight values in the periodic table, and their application

2 Note well that atomic masses are RELATIVE MASSES of atoms - all compared to the mass of an atom of carbon-12 (the isotope with 6 protons and 6 neutrons) which is assigned a mass of amu. What could a comparison of Atomic Weights of two elements be called? A ratio? But isn't that a conversion factor? Yes, a conversion factor that shows the relative weights of atoms for two elements. Given that an atom of tellurium (Te, at.no. = 52) has a standard mass of , and that an atom of scandium (Sc, at.no. = 21) has a standard mass of 44.96, compare the relative weights of these two atoms. [ mass of one Te atom].. [ mass of one Sc atom ] = = Conclude that one tellurium atom is times heavier than one scandium atom (or a scandium atom is 1 / or times the mass of a tellurium atom). Now let's change our point of view. Suppose that a quantity of tellurium weighing grams is placed in a beaker. Secondly, suppose that a quantity of scandium weighing grams is placed in a flask. The quantity of tellurium compared to scandium is greater by a factor of [ ] g / g = / 1. What can be concluded about the number of tellurium atoms in the beaker compared to scandium atoms in the flask? (Both contain the same number of atoms.) GRAM quantities of elements or compounds - equal in mass to their standard mass - contain the same number of items. This particular quantity of an element or compound is identified as ONE MOLE of the substance. So: ONE MOLE of all substances contain the SAME NUMBER of items, and ONE MOLE of a chemical substance has a weight (in grams) equal to its standard weight Moles is... (pardon the English) The CONCEPT of moles is comparable to CONCEPTS of percentages and fractions. CONCEPTS of percent and fraction never change. They are always "part over whole". However the VALUES of "part over whole" change depending on the magnitudes of the two items. Thus we meet sales with 10% off, 25 % discount, 1/3 off,... But in every case, it's always "part compared to whole". Similarly, the CONCEPT of moles never changes. It is always "a given mass over the standard mass". However, as noted above, the VALUES of "a given mass over the standard mass" change depending on magnitudes of the given mass and the standard mass of the substance. Thus we meet moles, 2.75 moles, 3.76 x 10-4 moles... But in every case, it's always "a given mass compared to the standard mass". When the part equals the whole then we have 100 %, and the same is true for the fraction of 1 / 1, or in decimal form. Similarly, when the given mass equals the standard mass then we have ONE mole of the substance. However, ONE mole is just a point on a continuum of values. Chemical formulas show ratios of moles of elements present in the compound.

3 An Elemental Symbol, what does it mean? Zr this symbol can represent... from a microscopic view one atom (a number) amu* (mass of one atom) *amu = 10. gram 6. 20x10 23 from a macroscopic view one mole of atoms (a number) grams (mass of a mole of atoms) A Chemical Formula, what does it mean? C 27 H 48 O this symbol can represent... from a microscopic view one molecule (a number) 386 amu* (mass of one molecule) from a macroscopic view one mole of molecules (a number) 386 grams (mass of a mole of molecules)

4 Atomic Weights show relative weights of atoms, all compared to the C-12 isotope. How much heavier / lighter is a* phosphorus atom (has standard mass of amu) magesium atom (has standard mass of amu) weight ratio = or, heavier Why is a phosphorus atom heavier than a magnesium atom? Consider a 50.0 g mass of phosphorus, and a separate 50.0 g mass of magnesium. What can be said about these two quantities. One of these two quantities contains MORE ATOMS than the other. Which substance contains more atoms? How many more atoms does it contain, compared to the other?

5 D. How much heavier is a phosphorus atom when compared to a magnesium atom? (Express this as a ratio, not a difference) Compare standard masses. Phosphorus atom is times heavier than a magnesium atom. mass phosphorus mass magnesium = = E. What mass of silicon will contain the same number of atoms as grams of zinc? The standard mass of zinc = This quantity of zinc (in grams) will contain the same number of atoms as the standard mass of silicon (in grams), which would be grams. So g of Si and g of Zn both contain the same number of atoms. F. What mass of chromium will contain 3.85 times as many atoms as are present in 6.29 grams of boron? Clearly, g chromium and g boron contain the same number of atoms. Use this information to find a similar relation for chromium and 6.29 grams of boron.. g Cr? g Cr = gb g B = g Cr, and then multiply this by 3.85 to get g of chromium. 2. Chemical Stoichiometry determining empirical formulas (based on simplest integer ratio of moles) Reversing the procedure used above to find per cent compositions yields a certain kind of chemical formula. However, it may differ from the actual formula of a molecular compound. It is called an empirical formula. All chemical formulas display ratios of moles of elements present in the compound (as ratios of subscripts), but empirical formulas can only convey the simplest integer ratio of moles of elements. A. Toluene is composed of the elements carbon and hydrogen, and chemical analysis shows a composition of % carbon. What is the empirical formula of toluene? B. An ionic compound is analyzed and found to contain % strontium, % nitrogen, and the remainder is oxygen. What is the empirical formula of the compound? For ionic compounds, the simplest formula is the only formula that can be determined. (Why?) But for molecular compounds, simplest formulas can be some sub-multiple of the molecular formula. The empirical formula could be 1/2, 1/3, 1/4, of the actual molecular formula. To determine a molecular formula requires knowledge of the molecular weight of the compound. Experimental methods for finding molecular weights are few and precious. They represent an important feature in chemistry and we'll note them well in this course. Consider an example of finding an empirical formula, and then proceeding to the molecular formula - when the standard weight is known or given. C. The flavor of oranges is due to a compound composed of elements C, H, and O, and that has a molecular weight of 172 grams / mole. Combustion of g of the compound in xs oxygen yields g of carbon dioxide, and g of water. Determine the empirical formula, and also determine the molecular formula.

6 1. A. Combining weights inform that so many grams of X always combines with so many grams of Y; they are as good an expression of the Law of Constant Composition as is any analytical information. mass Ca = g percent Ca is: mass Cl = mass cmpd - mass Ca = = g what part of the whole is due to Ca? % Ca = / = % percent Cl is: what part of the whole is due to Cl? % Cl = / = % B. mass Hg = g mass O = mass cmpd - mass Hg = = 1.71 g percent Hg is: what part of the whole is due to Hg? % Hg = / = % percent O is: what part of the whole is due to O? C. In a combustion reaction, % O = 1.71 / = 8.00 % all of the carbon present in the original compound is completely converted to carbon dioxide, and all of the hydrogen present in the original compound is completely converted to water. This reaction occurs in the presence of an excess of oxygen gas. Consequently, it is not possible to determine anything about the amount of oxygen that might be present in the original compound g cmpd (C, H, O) --> g CO 2 and g H 2 O In order to find what part of the whole compound is due to carbon, hydrogen, and oxygen (i.e., to determine its composition) first requires finding the carbon present in g of CO 2, the hydrogen present in g of H 2 O, and so on. So, the first question to ask is, what part of carbon dioxide is due to carbon (and so on).? g C = g CO 2? g H = g H 2 O 12 g C 44 g CO 2 2 g H 18 g H2O = g carbon = g hydrogen

7 mass oxygen is obtained by difference:? g O = mass cmpd - ( C + H ) = ( ) = g oxygen The composition of this benzoic acid follows as: % C = / = % % H = / = 5.02 % % O = / = % 2. Chemical formulas show ratios of moles of elements present in the compound, and are of two types; (a) EMPIRICAL FORMULAS show the most simple integer ratio, and (b) MOLECULAR FORMULAS ( the actual formulas for molecular compounds) which are some multiple of the empirical formula. Recall that moles is "a given mass over the standard mass". A. Toluene consists of % carbon and (by difference) 8.70 % hydrogen. Since formulas are ratios of moles, express the given (mass) composition as moles... What part of its standard weight is a given mass of g carbon?? moles C = g 1mole 12 g C = moles carbon What part of its standard weight is a given mass of 8.70 g hydrogen?? moles H = 8.70 g 1 mole H 1 g H = 8.70 moles hydrogen At this point the following formula could be written: C H 8.70 However, an integer ratio of moles is sought, so divide both mole quantities by the smaller value of This results in a formula of... C H Now what? Round off? Absolutely not! Recognize that there are four significant figures in the given information (91.30). Make use of all of them. So find two integers (to FOUR digits) that are related to both and One way of accomplishing this is to set-up a multiplication table involving the two values and a sequential set of integers. In class the use of the EXCEL spreadsheet was demonstrated for finding the two integers.

8 CARBON HYDROGEN x 1 = 2 2 x = x 1 = 3 3 x = x 1 = 4 4 x = x 1 = 5 5 x = x 1 = 6 6 x = x 1 = 7 7 x = x 1 = 8 8 x 1,143 = etc. etc. Conclude that the mole ratio to is the same as the integer ratio of 7 to 8. So the simplest / empirical formula of toluene is: C 7 H 8 The molecular formula cannot be determined from information available in this problem. However, the molecular formula of toluene would be some integer multiple (1, 2, 3...) of this empirical formula. 2. B. mass percents are given: Sr = g N = g O = g A chemical formula shows the ratio of moles of elements present in the compound. Express these masses as mole quantities... 1 mole Sr? moles Sr = g Sr g Sr 1 molen? moles N = g N 14 g N? moles O = g O 1 mole O 16 g O For starters, express the formula as: = moles Sr = moles N = moles O Sr N O divide all by to yield: Sr N 2 O 4 2. C. Combustion is the chemical reaction of a substance with molecular oxygen. In this case the molecular weight is given so the molecular formula can be determined. In addition, a balanced equation will be written for the combustion reaction after determination of the molecular formula. Given: g (C, H, O) forms g CO 2 and g H 2 O Note that the original compound contains oxygen, AND oxygen is also a reactant here. Because there are two sources of oxygen it is not possible to determine the mass of oxygen directly. It must be found indirectly, by first finding masses of carbon and hydrogen present in CO 2 and H 2 O, and then find the mass they (C and H) do not account for in the original compound.

9 ? g C = g CO 2? g H = g H 2 O 12 g C 44 g CO 2 2 g H 18 g H2O = g carbon = g hydrogen mass oxygen is obtained by adding mass C and H, and then subtracting from mass of the original compound:? g O = mass cmpd - ( C + H ) = ( ) = g oxygen Chemical formulas show ratios of moles of elements in compounds. So express these masses as moles...? moles C = g C 1 mole C 12 g C = moles C? moles H = g H 1 mole H 1 g H = moles C? mole O = g O 1 mole O 16 g O = moles O The initial formula can be written as: C H O Dividing by the smaller moles value (0.0248) yields the formula: C 5.00 H O 1.00 Which can be reasonably rounded off to integer values: C 5 H 10 O 1 The sum of standard weights in this empirical formula (i.e., the empirical formula weight ) is: 5 x x x 16 = 86. Recall that the molecular weight was givan as 172 g/mole. Clearly the molecular weight is TWICE the empirical weight, so the actual molecule must have TWICE the number of atoms as are present in the empirical formula. Thus the molecular formula is: C 10 H 20 O 2 (having a MW = 172 g / mole) and the balanced chemical equation for this combustion reaction would be... C 10 H 20 O 2 (s) + 14 O 2 (g) = 10 CO 2 (g) + 10 H 2 O (g)

Chem 115 POGIL Worksheet - Week 4 Moles & Stoichiometry

Chem 115 POGIL Worksheet - Week 4 Moles & Stoichiometry Chem 115 POGIL Worksheet - Week 4 Moles & Stoichiometry Why? Chemists are concerned with mass relationships in chemical reactions, usually run on a macroscopic scale (grams, kilograms, etc.). To deal with

More information

The Mole Concept. The Mole. Masses of molecules

The Mole Concept. The Mole. Masses of molecules The Mole Concept Ron Robertson r2 c:\files\courses\1110-20\2010 final slides for web\mole concept.docx The Mole The mole is a unit of measurement equal to 6.022 x 10 23 things (to 4 sf) just like there

More information

Chapter 3: Stoichiometry

Chapter 3: Stoichiometry Chapter 3: Stoichiometry Goal is to understand and become proficient at working with: 1. Avogadro's Number, molar mass and converting between mass and moles (REVIEW). 2. empirical formulas from analysis.

More information

Chapter 3: Stoichiometry

Chapter 3: Stoichiometry Chapter 3: Stoichiometry Key Skills: Balance chemical equations Predict the products of simple combination, decomposition, and combustion reactions. Calculate formula weights Convert grams to moles and

More information

Mass and Moles of a Substance

Mass and Moles of a Substance Chapter Three Calculations with Chemical Formulas and Equations Mass and Moles of a Substance Chemistry requires a method for determining the numbers of molecules in a given mass of a substance. This allows

More information

Formulas, Equations, and Moles. + "reacts with" "to produce" Equations must be balanced. Equal amounts of each element on each side of the equation.

Formulas, Equations, and Moles. + reacts with to produce Equations must be balanced. Equal amounts of each element on each side of the equation. Chapter 3 Formulas, Equations, and Moles Chemical Equations 2 2 + 2 2 2 reactants products + "reacts with" "to produce" coefficients - indicate amount of substance Equations must be balanced. Equal amounts

More information

Atomic Masses. Chapter 3. Stoichiometry. Chemical Stoichiometry. Mass and Moles of a Substance. Average Atomic Mass

Atomic Masses. Chapter 3. Stoichiometry. Chemical Stoichiometry. Mass and Moles of a Substance. Average Atomic Mass Atomic Masses Chapter 3 Stoichiometry 1 atomic mass unit (amu) = 1/12 of the mass of a 12 C atom so one 12 C atom has a mass of 12 amu (exact number). From mass spectrometry: 13 C/ 12 C = 1.0836129 amu

More information

Chemical Calculations: The Mole Concept and Chemical Formulas. AW Atomic weight (mass of the atom of an element) was determined by relative weights.

Chemical Calculations: The Mole Concept and Chemical Formulas. AW Atomic weight (mass of the atom of an element) was determined by relative weights. 1 Introduction to Chemistry Atomic Weights (Definitions) Chemical Calculations: The Mole Concept and Chemical Formulas AW Atomic weight (mass of the atom of an element) was determined by relative weights.

More information

Chemical Proportions in Compounds

Chemical Proportions in Compounds Chapter 6 Chemical Proportions in Compounds Solutions for Practice Problems Student Textbook page 201 1. Problem A sample of a compound is analyzed and found to contain 0.90 g of calcium and 1.60 g of

More information

Subscripts and Coefficients Give Different Information

Subscripts and Coefficients Give Different Information Chapter 3: Stoichiometry Goal is to understand and become proficient at working with: 1. Chemical equations (Balancing REVIEW) 2. Some simple patterns of reactivity 3. Formula weights (REVIEW) 4. Avogadro's

More information

3 large lures x 22.0 g/lure + 5 medium lures x 12.9 g/lure + 5 small lures x 8.5 g/lure g packaging = g

3 large lures x 22.0 g/lure + 5 medium lures x 12.9 g/lure + 5 small lures x 8.5 g/lure g packaging = g Answers additional questions 7.1 1. Describe how the particles of sodium bromide, an ionic compound, are different from water, a covalent compound. Give the particle name of each compound type. Ionic compounds

More information

TOPIC 8. CHEMICAL CALCULATIONS II: % composition, empirical formulas.

TOPIC 8. CHEMICAL CALCULATIONS II: % composition, empirical formulas. TOPIC 8. CHEMICAL CALCULATIONS II: % composition, empirical formulas. Percentage composition of elements in compounds. In Topic 1 it was stated that a given compound always has the same composition by

More information

Honors Chemistry: Unit 6 Test Stoichiometry PRACTICE TEST ANSWER KEY Page 1. A chemical equation. (C-4.4)

Honors Chemistry: Unit 6 Test Stoichiometry PRACTICE TEST ANSWER KEY Page 1. A chemical equation. (C-4.4) Honors Chemistry: Unit 6 Test Stoichiometry PRACTICE TEST ANSWER KEY Page 1 1. 2. 3. 4. 5. 6. Question What is a symbolic representation of a chemical reaction? What 3 things (values) is a mole of a chemical

More information

CHEMICAL FORMULA COEFFICIENTS AND SUBSCRIPTS. Chapter 3: Molecular analysis 3O 2 2O 3

CHEMICAL FORMULA COEFFICIENTS AND SUBSCRIPTS. Chapter 3: Molecular analysis 3O 2 2O 3 Chapter 3: Molecular analysis Read: BLB 3.3 3.5 H W : BLB 3:21a, c, e, f, 25, 29, 37,49, 51, 53 Supplemental 3:1 8 CHEMICAL FORMULA Formula that gives the TOTAL number of elements in a molecule or formula

More information

EMPIRICAL AND MOLECULAR FORMULA

EMPIRICAL AND MOLECULAR FORMULA EMPIRICAL AND MOLECULAR FORMULA Percent Composition: law of constant composition states that any sample of a pure compound always consists of the same elements combined in the same proportions by mass

More information

Chem 115 POGIL Worksheet - Week 4 Moles & Stoichiometry Answers

Chem 115 POGIL Worksheet - Week 4 Moles & Stoichiometry Answers Key Questions & Exercises Chem 115 POGIL Worksheet - Week 4 Moles & Stoichiometry Answers 1. The atomic weight of carbon is 12.0107 u, so a mole of carbon has a mass of 12.0107 g. Why doesn t a mole of

More information

Stoichiometry Dr. M. E. Bridge

Stoichiometry Dr. M. E. Bridge Preliminary Chemistry Course Stoichiometry Dr. M. E. Bridge What is stoichiometry? The meaning of the word: The word stoichiometry comes from two Greek words: (meaning element ) and (meaning measure )

More information

4. Magnesium has three natural isotopes with the following masses and natural abundances:

4. Magnesium has three natural isotopes with the following masses and natural abundances: Exercise #1 Atomic Masses 1. The average mass of pennies minted after 1982 is 2.50 g and the average mass of pennies minted before 1982 is 3.00 g. In a sample that contains 90.0% new and 10.0% old pennies,

More information

Practice questions for Ch. 3

Practice questions for Ch. 3 Name: Class: Date: ID: A Practice questions for Ch. 3 1. A hypothetical element consists of two isotopes of masses 69.95 amu and 71.95 amu with abundances of 25.7% and 74.3%, respectively. What is the

More information

Chapter 3. Stoichiometry: Ratios of Combination. Insert picture from First page of chapter. Copyright McGraw-Hill 2009 1

Chapter 3. Stoichiometry: Ratios of Combination. Insert picture from First page of chapter. Copyright McGraw-Hill 2009 1 Chapter 3 Insert picture from First page of chapter Stoichiometry: Ratios of Combination Copyright McGraw-Hill 2009 1 3.1 Molecular and Formula Masses Molecular mass - (molecular weight) The mass in amu

More information

The mass of the formula unit is called the formula mass Formula masses are calculated the same way as molecular masses

The mass of the formula unit is called the formula mass Formula masses are calculated the same way as molecular masses Chapter 4: The Mole Atomic mass provides a means to count atoms by measuring the mass of a sample The periodic table on the inside cover of the text gives atomic masses of the elements The mass of an atom

More information

Useful only for measuring the mass of very small objects atoms and molecules!

Useful only for measuring the mass of very small objects atoms and molecules! Chapter 9 Chemical Composition (Moles) Which weighs more, 1 atom of He or 1 atom of O? Units of mass: Pound Kilogram Atomic mass unit (AMU) There are others! 1 amu = 1.66 x 10-24 grams = mass of a proton

More information

Chem 31 Fall 2002. Chapter 3. Stoichiometry: Calculations with Chemical Formulas and Equations. Writing and Balancing Chemical Equations

Chem 31 Fall 2002. Chapter 3. Stoichiometry: Calculations with Chemical Formulas and Equations. Writing and Balancing Chemical Equations Chem 31 Fall 2002 Chapter 3 Stoichiometry: Calculations with Chemical Formulas and Equations Writing and Balancing Chemical Equations 1. Write Equation in Words -you cannot write an equation unless you

More information

Stoichiometry. What is the atomic mass for carbon? For zinc?

Stoichiometry. What is the atomic mass for carbon? For zinc? Stoichiometry Atomic Mass (atomic weight) Atoms are so small, it is difficult to discuss how much they weigh in grams We use atomic mass units an atomic mass unit (AMU) is one twelfth the mass of the catbon-12

More information

Chemical Proportions in Compounds

Chemical Proportions in Compounds Chapter 3 Chemical Proportions in Compounds Note to teacher: You will notice that there are two different formats for the Sample Problems in the student textbook. Where appropriate, the Sample Problem

More information

Part One: Mass and Moles of Substance. Molecular Mass = sum of the Atomic Masses in a molecule

Part One: Mass and Moles of Substance. Molecular Mass = sum of the Atomic Masses in a molecule CHAPTER THREE: CALCULATIONS WITH CHEMICAL FORMULAS AND EQUATIONS Part One: Mass and Moles of Substance A. Molecular Mass and Formula Mass. (Section 3.1) 1. Just as we can talk about mass of one atom of

More information

KEY for Unit 1 Your Chemical Toolbox: Scientific Concepts, Fundamentals of Typical Calculations, the Atom and Much More

KEY for Unit 1 Your Chemical Toolbox: Scientific Concepts, Fundamentals of Typical Calculations, the Atom and Much More KEY for Unit 1 Your Chemical Toolbox: Scientific Concepts, Fundamentals of Typical Calculations, the Atom and Much More The Modern Periodic Table The Periodic Law - when elements are arranged according

More information

Chapter 3. Chemical Reactions and Reaction Stoichiometry. Lecture Presentation. James F. Kirby Quinnipiac University Hamden, CT

Chapter 3. Chemical Reactions and Reaction Stoichiometry. Lecture Presentation. James F. Kirby Quinnipiac University Hamden, CT Lecture Presentation Chapter 3 Chemical Reactions and Reaction James F. Kirby Quinnipiac University Hamden, CT The study of the mass relationships in chemistry Based on the Law of Conservation of Mass

More information

Calculating Atoms, Ions, or Molecules Using Moles

Calculating Atoms, Ions, or Molecules Using Moles TEKS REVIEW 8B Calculating Atoms, Ions, or Molecules Using Moles TEKS 8B READINESS Use the mole concept to calculate the number of atoms, ions, or molecules in a sample TEKS_TXT of material. Vocabulary

More information

Name Date Class CHEMICAL QUANTITIES. SECTION 10.1 THE MOLE: A MEASUREMENT OF MATTER (pages 287 296)

Name Date Class CHEMICAL QUANTITIES. SECTION 10.1 THE MOLE: A MEASUREMENT OF MATTER (pages 287 296) Name Date Class 10 CHEMICAL QUANTITIES SECTION 10.1 THE MOLE: A MEASUREMENT OF MATTER (pages 287 296) This section defines the mole and explains how the mole is used to measure matter. It also teaches

More information

Chemical calculations

Chemical calculations Chemical calculations Stoichiometry refers to the quantities of material which react according to a balanced chemical equation. Compounds are formed when atoms combine in fixed proportions. E.g. 2Mg +

More information

CHEMICAL QUANTITIES. Chapter 10

CHEMICAL QUANTITIES. Chapter 10 CHEMICAL QUANTITIES Chapter 10 What is a mole? A unit of measurement in chemistry 1 mole of a substance = 6.02 x 10 23 (Avagadro s number) representative particles of a substance Representative particle

More information

Chapter 6 Chemical Calculations

Chapter 6 Chemical Calculations Chapter 6 Chemical Calculations 1 Submicroscopic Macroscopic 2 Chapter Outline 1. Formula Masses (Ch 6.1) 2. Percent Composition (supplemental material) 3. The Mole & Avogadro s Number (Ch 6.2) 4. Molar

More information

Chapter 3 Chemical Reactions and Reaction Stoichiometry. 許富銀 ( Hsu Fu-Yin)

Chapter 3 Chemical Reactions and Reaction Stoichiometry. 許富銀 ( Hsu Fu-Yin) Chapter 3 Chemical Reactions and Reaction Stoichiometry 許富銀 ( Hsu Fu-Yin) 1 Stoichiometry The study of the numerical relationship between chemical quantities in a chemical reaction is called stoichiometry.

More information

Chapter 4 Chemical Equations & Stoichiometry

Chapter 4 Chemical Equations & Stoichiometry Chapter 4 Chemical Equations & Stoichiometry Chemical reactions are best described using equations which tells us what compounds we started with (reactants), what we did to them (reaction conditions) and

More information

Lecture Notes Chemistry E-1. Chapter 3

Lecture Notes Chemistry E-1. Chapter 3 Lecture Notes Chemistry E-1 Chapter 3 http://inserbia.info/news/wp-content/uploads/2013/05/tamiflu.jpg http://nutsforhealthcare.files.wordpress.com/2013/01/tamiflu-moa.jpg The Mole A mole is a certain

More information

Chapter 7. Bellringer. Table of Contents. Chapter 7. Chapter 7. Objectives. Avogadro s Number and the Mole. Chapter 7. Chapter 7

Chapter 7. Bellringer. Table of Contents. Chapter 7. Chapter 7. Objectives. Avogadro s Number and the Mole. Chapter 7. Chapter 7 The Mole and Chemical Table of Contents Chemical Formulas Bellringer List as many common counting units as you can. Determine how many groups of each unit in your list are present in each of the following

More information

CHAPTER 11 - CHEMICAL QUANTITIES

CHAPTER 11 - CHEMICAL QUANTITIES I. THE MOLE CONCEPT CHAPTER 11 - CHEMICAL QUANTITIES A. What is a mole? 1. a mole is the SI unit of measurement of counting; just like a dozen is a measurement 2. a mole is a number a. 6.02 x 10 23 is

More information

Chapter 1: Moles and equations. Learning outcomes. you should be able to:

Chapter 1: Moles and equations. Learning outcomes. you should be able to: Chapter 1: Moles and equations 1 Learning outcomes you should be able to: define and use the terms: relative atomic mass, isotopic mass and formula mass based on the 12 C scale perform calculations, including

More information

IB Chemistry 1 Mole. One atom of C-12 has a mass of 12 amu. One mole of C-12 has a mass of 12 g. Grams we can use more easily.

IB Chemistry 1 Mole. One atom of C-12 has a mass of 12 amu. One mole of C-12 has a mass of 12 g. Grams we can use more easily. The Mole Atomic mass units and atoms are not convenient units to work with. The concept of the mole was invented. This was the number of atoms of carbon-12 that were needed to make 12 g of carbon. 1 mole

More information

Other Stoich Calculations A. mole mass (mass mole) calculations. GIVEN mol A x CE mol B. PT g A CE mol A MOLE MASS :

Other Stoich Calculations A. mole mass (mass mole) calculations. GIVEN mol A x CE mol B. PT g A CE mol A MOLE MASS : Chem. I Notes Ch. 12, part 2 Using Moles NOTE: Vocabulary terms are in boldface and underlined. Supporting details are in italics. 1 MOLE = 6.02 x 10 23 representative particles (representative particles

More information

Chemical Calculations: Formula Masses, Moles, and Chemical Equations

Chemical Calculations: Formula Masses, Moles, and Chemical Equations Chemical Calculations: Formula Masses, Moles, and Chemical Equations Atomic Mass & Formula Mass Recall from Chapter Three that the average mass of an atom of a given element can be found on the periodic

More information

Chapter 8 How to Do Chemical Calculations

Chapter 8 How to Do Chemical Calculations Chapter 8 How to Do Chemical Calculations Chemistry is both a qualitative and a quantitative science. In the laboratory, it is important to be able to measure quantities of chemical substances and, as

More information

Chemical Composition Review Mole Calculations Percent Composition. Copyright Cengage Learning. All rights reserved. 8 1

Chemical Composition Review Mole Calculations Percent Composition. Copyright Cengage Learning. All rights reserved. 8 1 Chemical Composition Review Mole Calculations Percent Composition Copyright Cengage Learning. All rights reserved. 8 1 QUESTION Suppose you work in a hardware store and a customer wants to purchase 500

More information

The Nature of Chemistry

The Nature of Chemistry CHAPTER 1 The Nature of Chemistry Objectives You will be able to do the following. 1. Describe how science in general is done. 2. Given a description of a property of a substance, identify the property

More information

1. How many hydrogen atoms are in 1.00 g of hydrogen?

1. How many hydrogen atoms are in 1.00 g of hydrogen? MOLES AND CALCULATIONS USING THE MOLE CONCEPT INTRODUCTORY TERMS A. What is an amu? 1.66 x 10-24 g B. We need a conversion to the macroscopic world. 1. How many hydrogen atoms are in 1.00 g of hydrogen?

More information

Chapter 3 Calculation with Chemical Formulas and Equations

Chapter 3 Calculation with Chemical Formulas and Equations Chapter 3 Calculation with Chemical Formulas and Equations Practical Applications of Chemistry Determining chemical formula of a substance Predicting the amount of substances consumed during a reaction

More information

Unit 3 Notepack Chapter 7 Chemical Quantities Qualifier for Test

Unit 3 Notepack Chapter 7 Chemical Quantities Qualifier for Test Unit 3 Notepack Chapter 7 Chemical Quantities Qualifier for Test NAME Section 7.1 The Mole: A Measurement of Matter A. What is a mole? 1. Chemistry is a quantitative science. What does this term mean?

More information

Matter. Atomic weight, Molecular weight and Mole

Matter. Atomic weight, Molecular weight and Mole Matter Atomic weight, Molecular weight and Mole Atomic Mass Unit Chemists of the nineteenth century realized that, in order to measure the mass of an atomic particle, it was useless to use the standard

More information

Concept 1. The meaning and usefulness of the mole. The mole (or mol) represents a certain number of objects.

Concept 1. The meaning and usefulness of the mole. The mole (or mol) represents a certain number of objects. Chapter 3. Stoichiometry: Mole-Mass Relationships in Chemical Reactions Concept 1. The meaning and usefulness of the mole The mole (or mol) represents a certain number of objects. SI def.: the amount of

More information

Mole Notes.notebook. October 29, 2014

Mole Notes.notebook. October 29, 2014 1 2 How do chemists count atoms/formula units/molecules? How do we go from the atomic scale to the scale of everyday measurements (macroscopic scale)? The gateway is the mole! But before we get to the

More information

Chapter 3 Stoichiometry Mole - Mass Relationships in Chemical Systems

Chapter 3 Stoichiometry Mole - Mass Relationships in Chemical Systems Chapter 3 Stoichiometry Mole - Mass Relationships in Chemical Systems 3.1 Atomic Masses 3.2 The Mole 3.3 Molar Mass 3.4 Percent Composition of Compounds 3.5 Determining the Formula of a Compound 3.6 Chemical

More information

PERIODIC TABLE OF ELEMENTS. 4/23/14 Chapter 7: Chemical Reactions 1

PERIODIC TABLE OF ELEMENTS. 4/23/14 Chapter 7: Chemical Reactions 1 PERIODIC TABLE OF ELEMENTS 4/23/14 Chapter 7: Chemical Reactions 1 CHAPTER 7: CHEMICAL REACTIONS 7.1 Describing Reactions 7.2 Types of Reactions 7.3 Energy Changes in Reactions 7.4 Reaction Rates 7.5 Equilibrium

More information

CHEM 105 HOUR EXAM III 28-OCT-99. = -163 kj/mole determine H f 0 for Ni(CO) 4 (g) = -260 kj/mole determine H f 0 for Cr(CO) 6 (g)

CHEM 105 HOUR EXAM III 28-OCT-99. = -163 kj/mole determine H f 0 for Ni(CO) 4 (g) = -260 kj/mole determine H f 0 for Cr(CO) 6 (g) CHEM 15 HOUR EXAM III 28-OCT-99 NAME (please print) 1. a. given: Ni (s) + 4 CO (g) = Ni(CO) 4 (g) H Rxn = -163 k/mole determine H f for Ni(CO) 4 (g) b. given: Cr (s) + 6 CO (g) = Cr(CO) 6 (g) H Rxn = -26

More information

The Mole Concept. A. Atomic Masses and Avogadro s Hypothesis

The Mole Concept. A. Atomic Masses and Avogadro s Hypothesis The Mole Concept A. Atomic Masses and Avogadro s Hypothesis 1. We have learned that compounds are made up of two or more different elements and that elements are composed of atoms. Therefore, compounds

More information

The Mole. 6.022 x 10 23

The Mole. 6.022 x 10 23 The Mole 6.022 x 10 23 Background: atomic masses Look at the atomic masses on the periodic table. What do these represent? E.g. the atomic mass of Carbon is 12.01 (atomic # is 6) We know there are 6 protons

More information

Simple vs. True. Simple vs. True. Calculating Empirical and Molecular Formulas

Simple vs. True. Simple vs. True. Calculating Empirical and Molecular Formulas Calculating Empirical and Molecular Formulas Formula writing is a key component for success in chemistry. How do scientists really know what the true formula for a compound might be? In this lesson we

More information

Study Guide For Chapter 7

Study Guide For Chapter 7 Name: Class: Date: ID: A Study Guide For Chapter 7 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. The number of atoms in a mole of any pure substance

More information

Chapter 1 The Atomic Nature of Matter

Chapter 1 The Atomic Nature of Matter Chapter 1 The Atomic Nature of Matter 6. Substances that cannot be decomposed into two or more simpler substances by chemical means are called a. pure substances. b. compounds. c. molecules. d. elements.

More information

The Empirical Formula of a Compound

The Empirical Formula of a Compound The Empirical Formula of a Compound Lab #5 Introduction A look at the mass relationships in chemistry reveals little order or sense. The ratio of the masses of the elements in a compound, while constant,

More information

Chapter Three: STOICHIOMETRY

Chapter Three: STOICHIOMETRY p70 Chapter Three: STOICHIOMETRY Contents p76 Stoichiometry - The study of quantities of materials consumed and produced in chemical reactions. p70 3-1 Counting by Weighing 3-2 Atomic Masses p78 Mass Mass

More information

Stoichiometry. Lecture Examples Answer Key

Stoichiometry. Lecture Examples Answer Key Stoichiometry Lecture Examples Answer Key Ex. 1 Balance the following chemical equations: 3 NaBr + 1 H 3 PO 4 3 HBr + 1 Na 3 PO 4 2 C 3 H 5 N 3 O 9 6 CO 2 + 3 N 2 + 5 H 2 O + 9 O 2 2 Ca(OH) 2 + 2 SO 2

More information

Calculating Chemical Composition

Calculating Chemical Composition Calculating Chemical Composition A Directed Learning Activity for Hartnell College Chemistry 1 Funded by the Title V STEM Grant #P031S090007 through Hartnell College For information contact lyee@hartnell.edu

More information

Chemical Reactions. Chemical Equations. Mole as Conversion Factor: To convert between number of particles and an equivalent number of moles:

Chemical Reactions. Chemical Equations. Mole as Conversion Factor: To convert between number of particles and an equivalent number of moles: Quantities of Reactants and Products CHAPTER 3 Chemical Reactions Stoichiometry Application of The Law of Conservation of Matter Chemical book-keeping Chemical Equations Chemical equations: Describe proportions

More information

Name Date Class CHEMICAL QUANTITIES. SECTION 10.1 THE MOLE: A MEASUREMENT OF MATTER (pages 287 296)

Name Date Class CHEMICAL QUANTITIES. SECTION 10.1 THE MOLE: A MEASUREMENT OF MATTER (pages 287 296) 10 CHEMICAL QUANTITIES SECTION 10.1 THE MOLE: A MEASUREMENT OF MATTER (pages 287 296) This section defines the mole and explains how the mole is used to measure matter. It also teaches you how to calculate

More information

Chemistry I: Using Chemical Formulas. Formula Mass The sum of the average atomic masses of all elements in the compound. Units are amu.

Chemistry I: Using Chemical Formulas. Formula Mass The sum of the average atomic masses of all elements in the compound. Units are amu. Chemistry I: Using Chemical Formulas Formula Mass The sum of the average atomic masses of all elements in the compound. Units are amu. Molar Mass - The mass in grams of 1 mole of a substance. Substance

More information

Formulas, Equations and Moles

Formulas, Equations and Moles Chapter 3 Formulas, Equations and Moles Interpreting Chemical Equations You can interpret a balanced chemical equation in many ways. On a microscopic level, two molecules of H 2 react with one molecule

More information

MOLAR MASS AND MOLECULAR WEIGHT Themolar mass of a molecule is the sum of the atomic weights of all atoms in the molecule. Molar Mass.

MOLAR MASS AND MOLECULAR WEIGHT Themolar mass of a molecule is the sum of the atomic weights of all atoms in the molecule. Molar Mass. Counting Atoms Mg burns in air (O 2 ) to produce white magnesium oxide, MgO. How can we figure out how much oxide is produced from a given mass of Mg? PROBLEM: If If 0.200 g of Mg is is burned, how much

More information

How much does a single atom weigh? Different elements weigh different amounts related to what makes them unique.

How much does a single atom weigh? Different elements weigh different amounts related to what makes them unique. How much does a single atom weigh? Different elements weigh different amounts related to what makes them unique. What units do we use to define the weight of an atom? amu units of atomic weight. (atomic

More information

AP Chemistry. Unit #3. Chapter 3 Zumdahl

AP Chemistry. Unit #3. Chapter 3 Zumdahl AP Chemistry Unit #3 Chapter 3 Zumdahl Stoichiometry C6H12O6 + 6 O2 6 CO2 + 6 H2O Students should be able to: Calculate the atomic weight (average atomic mass) of an element from the relative abundances

More information

If you remember, we left off this part of the story with defining the mass of one 12

If you remember, we left off this part of the story with defining the mass of one 12 Chapter 11 Chemical Calculations For the past several weeks we have been working on our qualitative understanding of first atoms, then molecules, and finally chemical reactions. In this chapter we enter

More information

Chemistry 201. Quantitative Analysis

Chemistry 201. Quantitative Analysis Chemistry 201 Lecture 4 Quantitative Analysis NC State University Focus on energy The work done in the internal combustion engine is called pressure volume work. For a simple irreversible stroke the work

More information

MOLES AND MOLE CALCULATIONS

MOLES AND MOLE CALCULATIONS 35 MOLES ND MOLE CLCULTIONS INTRODUCTION The purpose of this section is to present some methods for calculating both how much of each reactant is used in a chemical reaction, and how much of each product

More information

Chapter 3! Stoichiometry: Calculations with Chemical Formulas and Equations. Stoichiometry

Chapter 3! Stoichiometry: Calculations with Chemical Formulas and Equations. Stoichiometry Chapter 3! : Calculations with Chemical Formulas and Equations Anatomy of a Chemical Equation CH 4 (g) + 2O 2 (g) CO 2 (g) + 2 H 2 O (g) Anatomy of a Chemical Equation CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2

More information

Lecture 5, The Mole. What is a mole?

Lecture 5, The Mole. What is a mole? Lecture 5, The Mole What is a mole? Moles Atomic mass unit and the mole amu definition: 12 C = 12 amu. The atomic mass unit is defined this way. 1 amu = 1.6605 x 10-24 g How many 12 C atoms weigh 12 g?

More information

AT Chapter 3 Notes 15.notebook. September 29, Measuring Atomic Masses

AT Chapter 3 Notes 15.notebook. September 29, Measuring Atomic Masses Measuring Atomic Masses Mass Spectrometer used to isolate isotopes of an element and determine their mass. 1 An element sample is heated to vaporize it and the gaseous atoms are zapped with an electron

More information

Chemistry 65 Chapter 6 THE MOLE CONCEPT

Chemistry 65 Chapter 6 THE MOLE CONCEPT THE MOLE CONCEPT Chemists find it more convenient to use mass relationships in the laboratory, while chemical reactions depend on the number of atoms present. In order to relate the mass and number of

More information

CHAPTER 7. Empirical Formulas

CHAPTER 7. Empirical Formulas CHAPTER 7 Empirical Formulas Suppose you analyze an unknown compound that is a white powder and find that it is composed of 36.5% sodium, 38.1% oxygen, and 25.4% sulfur. You can use those percentages to

More information

10.3 Percent Composition and Chemical Formulas. Chapter 10 Chemical Quantities Percent Composition and Chemical Formulas

10.3 Percent Composition and Chemical Formulas. Chapter 10 Chemical Quantities Percent Composition and Chemical Formulas Chapter 10 Chemical Quantities 101 The Mole: A Measurement of Matter 102 Mole-Mass and Mole-Volume Relationships 103 Percent Composition and Chemical Formulas 1 CHEMISTRY & YOU What does the percent composition

More information

MOLES, MOLECULES, FORMULAS. Part I: What Is a Mole And Why Are Chemists Interested in It?

MOLES, MOLECULES, FORMULAS. Part I: What Is a Mole And Why Are Chemists Interested in It? NAME PARTNERS SECTION DATE_ MOLES, MOLECULES, FORMULAS This activity is designed to introduce a convenient unit used by chemists and to illustrate uses of the unit. Part I: What Is a Mole And Why Are Chemists

More information

Chem 1100 Chapter Three Study Guide Answers Outline I. Molar Mass and Moles A. Calculations of Molar Masses

Chem 1100 Chapter Three Study Guide Answers Outline I. Molar Mass and Moles A. Calculations of Molar Masses Chem 1100 Chapter Three Study Guide Answers Outline I. Molar Mass and Moles A. Calculations of Molar Masses B. Calculations of moles C. Calculations of number of atoms from moles/molar masses 1. Avagadro

More information

Chapter 10 Chemical Quantities

Chapter 10 Chemical Quantities Chapter 10 Chemical Quantities 101 The Mole: A Measurement 102 Mole-Mass and Mole-Volume Relationships 103 Percent Composition and Chemical Formulas 1 Copyright Pearson Education, Inc, or its affiliates

More information

10 The Mole. Section 10.1 Measuring Matter

10 The Mole. Section 10.1 Measuring Matter Name Date Class The Mole Section.1 Measuring Matter In your textbook, read about counting particles. In Column B, rank the quantities from Column A from smallest to largest. Column A Column B 0.5 mol 1.

More information

The Mole and Molar Mass

The Mole and Molar Mass The Mole and Molar Mass 1 Molar mass is the mass of one mole of a substance. Molar mass is numerically equal to atomic mass, molecular mass, or formula mass. However the units of molar mass are g/mol.

More information

10.3 Percent Composition and Chemical Formulas

10.3 Percent Composition and Chemical Formulas Name Class Date 10.3 Percent Composition and Chemical Formulas Essential Understanding of its empirical formula. A molecular formula of a compound is a whole-number multiple Lesson Summary Percent Composition

More information

7.1 Stoichiometry and Percent Yield

7.1 Stoichiometry and Percent Yield score /10 pts. Name Class Date 7.1 Stoichiometry and Percent Yield Mole Ratios An example: The combustion of propane is used to heat many rural homes in winter. Balance the equation below for the combustion

More information

Balance the following equation: KClO 3 + C 12 H 22 O 11 KCl + CO 2 + H 2 O

Balance the following equation: KClO 3 + C 12 H 22 O 11 KCl + CO 2 + H 2 O Balance the following equation: KClO 3 + C 12 H 22 O 11 KCl + CO 2 + H 2 O Ans: 8 KClO 3 + C 12 H 22 O 11 8 KCl + 12 CO 2 + 11 H 2 O 3.2 Chemical Symbols at Different levels Chemical symbols represent

More information

7-5.5. Translate chemical symbols and the chemical formulas of common substances to show the component parts of the substances including:

7-5.5. Translate chemical symbols and the chemical formulas of common substances to show the component parts of the substances including: 7-5.5 Translate chemical symbols and the chemical formulas of common substances to show the component parts of the substances including: NaCl [salt], H 2 O [water], C 6 H 12 O 6 [simple sugar], O 2 [oxygen

More information

C2 Chemistry Calculations

C2 Chemistry Calculations C2 Chemistry Calculations You need to know how to carry out several calculations in Additional Science This booklet gives you a step by step guide to carrying out these equations and examples of each one.

More information

MOLE CONVERSION PROBLEMS. 2. How many moles are present in 34 grams of Cu(OH) 2? [0.35 moles]

MOLE CONVERSION PROBLEMS. 2. How many moles are present in 34 grams of Cu(OH) 2? [0.35 moles] MOLE CONVERSION PROBLEMS 1. What is the molar mass of MgO? [40.31 g/mol] 2. How many moles are present in 34 grams of Cu(OH) 2? [0.35 moles] 3. How many moles are present in 2.5 x 10 23 molecules of CH

More information

Atomic mass and the mole

Atomic mass and the mole Atomic mass and the mole An equation for a chemical reaction can provide us with a lot of useful information. It tells us what the reactants and the products are in the reaction, and it also tells us the

More information

Chem. Ch. 10 ~ THE MOLE NOTE: Vocabulary terms are in boldface and underlined. Supporting details are in italics.

Chem. Ch. 10 ~ THE MOLE NOTE: Vocabulary terms are in boldface and underlined. Supporting details are in italics. Chem. Ch. 10 ~ THE MOLE NOTE: Vocabulary terms are in boldface and underlined. Supporting details are in italics. 10.1 Notes I. Measuring Matter A. SI unit of chemical quantity = the mole (abbreviated

More information

Formulae, stoichiometry and the mole concept

Formulae, stoichiometry and the mole concept 3 Formulae, stoichiometry and the mole concept Content 3.1 Symbols, Formulae and Chemical equations 3.2 Concept of Relative Mass 3.3 Mole Concept and Stoichiometry Learning Outcomes Candidates should be

More information

Chapter 3 Stoichiometry of Formulas and Equations

Chapter 3 Stoichiometry of Formulas and Equations 3-1 Chapter 3 Stoichiometry of Formulas and Equations 3-2 Mole - Mass Relationships in Chemical Systems 3.1 The Mole 3.2 Determining the Formula of an Unknown Compound 3.3 Writing and Balancing Chemical

More information

CHEM 110: CHAPTER 3: STOICHIOMETRY: CALCULATIONS WITH CHEMICAL FORMULAS AND EQUATIONS

CHEM 110: CHAPTER 3: STOICHIOMETRY: CALCULATIONS WITH CHEMICAL FORMULAS AND EQUATIONS 1 CHEM 110: CHAPTER 3: STOICHIOMETRY: CALCULATIONS WITH CHEMICAL FORMULAS AND EQUATIONS The Chemical Equation A chemical equation concisely shows the initial (reactants) and final (products) results of

More information

2 Stoichiometry: Chemical Arithmetic Formula Conventions (1 of 24) 2 Stoichiometry: Chemical Arithmetic Stoichiometry Terms (2 of 24)

2 Stoichiometry: Chemical Arithmetic Formula Conventions (1 of 24) 2 Stoichiometry: Chemical Arithmetic Stoichiometry Terms (2 of 24) Formula Conventions (1 of 24) Superscripts used to show the charges on ions Mg 2+ the 2 means a 2+ charge (lost 2 electrons) Subscripts used to show numbers of atoms in a formula unit H 2 SO 4 two H s,

More information

The Atom Atomic Number Mass Number Isotopes

The Atom Atomic Number Mass Number Isotopes The Atom Atomic Number Mass Number Isotopes 1 Atomic Theory Atoms are building blocks of elements Similar atoms in each element Different from atoms of other elements Two or more different atoms bond in

More information

Notes: Formula Mass and Percent Composition

Notes: Formula Mass and Percent Composition Notes: Formula Mass and Percent Composition Formula mass - the mass of one mole of a compound, atom or ion. -also called: gram formula mass, molecular mass, gram molecular mass, formula weight, gram formula

More information

Element of same atomic number, but different atomic mass o Example: Hydrogen

Element of same atomic number, but different atomic mass o Example: Hydrogen Atomic mass: p + = protons; e - = electrons; n 0 = neutrons p + + n 0 = atomic mass o For carbon-12, 6p + + 6n 0 = atomic mass of 12.0 o For chlorine-35, 17p + + 18n 0 = atomic mass of 35.0 atomic mass

More information

Unit 6 The Mole Concept

Unit 6 The Mole Concept Chemistry Form 3 Page 62 Ms. R. Buttigieg Unit 6 The Mole Concept See Chemistry for You Chapter 28 pg. 352-363 See GCSE Chemistry Chapter 5 pg. 70-79 6.1 Relative atomic mass. The relative atomic mass

More information