Chapter 3. Mass Relationships in Chemical Reactions


 Camilla Holt
 2 years ago
 Views:
Transcription
1 Chapter 3 Mass Relationships in Chemical Reactions This chapter uses the concepts of conservation of mass to assist the student in gaining an understanding of chemical changes. Upon completion of Chapter 3, the student should be able to: 1) Convert between grams and atomic mass units (AMU s). 2) Calculate average atomic mass given the mass and natural abundance of each isotope. 3) Recall from memory Avogadro s number. 4) Determine the number of objects present in a given number of moles. 5) Convert between mass, number of moles, and number of atoms (molecules) of an element (compound). 6) Establish the molecular mass and molar mass given the molecular formula. 7) Sketch the main components of a mass spectrometer and comment on its use. 8) Compute the percent composition (mass percent) given the chemical formula for an ionic or molecular compound. 9) Describe the experimental procedure used to determine empirical formulas. 10) Establish the molecular formula given the mass of each element present (or mass percent of each element) and the compound s molar mass. 11) Balance chemical equations. 12) Interpret the meaning of chemical equations in terms of molecules, moles, and masses. 13) Distinguish between products and reactants in a chemical equation. 14) Predict the products formed by combustion reactions. 15) Use stoichiometric methods to predict the mass (number of moles) of the products formed given the mass of each reactant (number of moles of each reactant). 16) Use stoichiometric methods to deduce the limiting reagent, excess reagent, the amount of expected products produced, and the amount of excess reagent left over upon completion of the reaction given the mass (number of moles) of each reactant in the chemical equation. 17) Use stoichiometric methods to predict the theoretical yield and percent yield given the mass (number of moles) of each reactant and the actual yield of a reaction. 18) Calculate the mass (number of moles) of each reactant required given the percent yield and the mass (number of moles) of products desired. Section 3.1 Atomic Mass Sometimes atomic weight and atomic mass are used interchangeably; however, to decrease confusion and to be consistent, the term atomic weight is not used. The term atomic mass unit, or dalton, is an important concept for students who plan to enroll in materials science courses where the mass contained in a unit cell in the solid state is often determined. A helpful comparison can be made between calculating the average atomic mass and the semester grade for a course. For example, if 30% of the grade is based on the midterm, 20% on laboratory and 50% on the final and a student earns 80 on the midterm, 90 in laboratory, and a 96 on the final, the student s grade is (0.30) (80) + (0.20) (90) + (0.5) (96) = 90. A similar calculation can be done for the average atomic mass of Ne (see pages 74 and 75). Average molar mass of Ne = (0.9092) ( ) + ( ) ( ) + (0.0882) ( ) =20.2 g/mol
2 It is important for the student to think about the answer calculated. For example, if nearly 91% of Ne has a molar mass of g/mol and the other two isotopes have a larger mass, then 20.2 g/mol seems reasonable. Section 3.2 Molar Mass of an Element and Avogadro s Number A fundamental concept is that 1 mole = objects. One amu is defined as 1/12 the mass of one carbon12 atom. We define one mole of carbon12 ( carbon12 atoms) as 12 grams to get a molar mass of 12 g/mol. It is acceptable to say that the molar mass of carbon12 is 12 grams; however, if 12 g/mol is used consistently, the student will find it easier to solve problems using the factorlabel method introduced in Chapter 1. An error that students often make is to assume that since carbon12 is 12 amu and also 12 grams then 1 amu = 1 gram. This error is less likely if we use 12 amu/atom and 12 g/mol since it is obvious that 1 atom is not the same as a mole. For the conversion between amu and grams, it is useful to remind the student that it takes a very large number (Avogadro s Number, ) of amu to make one gram since the amu refers to an atom. Section 3.3 Molecular Mass As stated in Section 3.1, atomic mass and atomic weight are often used interchangeably. The same is true for molecular mass and molecular weight. Molecular mass is the correct term and should be used for consistency. In example 3.7, the factor 4 H atoms/1 molecule of (NH 2 ) 2 CO is used. Often this conversion is difficult for students to understand. If we start with a simpler example, maybe this concept will be easier. For example: How many oxygen atoms are there in one CO 2 molecule? (two oxygen atoms) How many oxygen atoms are there in one dozen CO 2 molecules? (two dozen or 24 oxygen atoms) How many oxygen atoms are there in one mole of CO 2 molecules? [two moles or 2( ) oxygen atoms] If that is clear, then how many hydrogen atoms are there in one molecule of (NH 2 ) 2 CO (four H atoms ) or how many H atoms in one mole of (NH 2 ) 2 CO [four moles or 4( ) H atoms] is easier to comprehend. Section 3.4 The Mass Spectrometer In Figure 3.3, it should be understood that the accelerating plates are negatively charged so that the positive ions will be accelerated toward them. See Section 3.1 of this manual for a discussion on calculating average molar mass. Section 3.5 Percent Composition of Compounds See Section 3.3 about a discussion on how to assist students in understanding the number of moles of an element in one mole of a compound.
3 In the Chemistry in Action section, Gold Fingerprinting by Mass Spectrometry, the mass spectrum shown does not include the mass spectrum of gold. Only Cd and Pb are shown to emphasize the relative abundance of these two trace elements in the gold specimen. Example 3.9 is representative of what is often done in the analysis of products formed by organic synthesis. The organic chemist makes a compound and has its empirical formula determined to give evidence that the product formed was the material desired. It should be noted that division by the smallest subscript forces at least one of the subscripts in the formula to be one. It should be recognized that 1.33 is really 4/3 thus CH O could be written as C 3/3 H 4/3 O 3/3 and the multiplication by three (the common denominator) will result in C 3 H 4 O 3. In a similar fashion, 1.66 would represent 5/3, 1.5 would represent 3/2, etc. Section 3.6 Experimental Determination of Empirical Formulas The study of ethanol s empirical formula assumes that ethanol contains only C, H, and O. If the sample contained something other than C, H, and O (sulfur, for example), then the assumption that the difference between the amount of the starting material (11.5 g ethanol) and the calculated masses of carbon and hydrogen in the ethanol (6.00 g and 1.51 g) to give the mass of oxygen in the sample would not be correct. In example 3.11, it may be useful to describe the following relationship: (empirical mass) (integer) = molar mass where empirical mass is the mass in grams of one mole of the material written as its empirical formula. Once the integer is found, it is used to multiply the subscripts of the empirical formula to obtain the molecular formula. For example, the empirical formula for acetylene is CH (13 g/mol is its empirical mass) while the molar mass of acetylene is 26 g/mol. Therefore (13 g/mol) (integer) = 26 g/mol integer = 2 the empirical formula, CH, becomes the molecular formula C 2 H 2. A similar example is benzene with its empirical formula of CH and its molar mass of 78 g/mol: (13 g/mol) (integer) = 78 g/mol integer = 6 so the empirical formula CH becomes the molecular formula C 6 H 6 when multiplied by six. Section 3.7 Chemical Reactions and Chemical Equations When chemical equations are balanced, it is assumed that equal numbers of atoms of a given element appear as reactants and products. This is a direct result of Dalton s atomic theory (Section 2.1) which states that chemical reactions involve the combination, separation, or rearrangement of atoms, but not the creation or destruction of atoms. Students learning how to balance chemical equations have a tendency to want to change
4 subscripts in the molecules; therefore, the first bullet on page 85 needs to be heavily stressed. The logic used to balance the O 2 in the combustion of C 2 H 6 often escapes students. Be sure to explain that 3.5 pairs of O 2 are needed to get the desired seven oxygen atoms as products. Note that the convention in this textbook is to use the smallest possible set of whole numbers in the balanced equation. Section 3.8 Amounts of Reactants and Products It is interesting to note that CO is a flammable gas. This point can have great implications in industrial settings that use CO. Figure 3.7 shows three common types of stoichiometric calculations. A fourth calculation may include number of molecules of reactant moles of reactant moles of product number of molecules of product The method of stringing factors along as shown in example 3.14 is used by many instructors who have a great deal of experience in solving this type of problem. However, many beginning students use the logic if A then B if B then C if C then D in problem solving; therefore, stringing out factors may be very confusing to them. It is suggested that the two methods be used interchangeably so that the student can see them both.
5 Section 3.9 Limiting Reagents Chemists often refer to limiting reagents, which confuses students because they have been working with products and reactants, not products and reagents. Be sure to explain that this is a convention which can be understood by substituting the word reactant for reagent. For the reaction: S(l) + 3F 2 (g) SF 6 (g) it would be better to express this as sulfur reacting with fluorine instead of sulfur burning in an atmosphere of fluorine because burning is often thought of as combining with O 2. The following fun example can be used to help students understand the concept of limiting reactants. We find a recipe for party cakes that requires one pint of milk and two eggs per cake. We have plenty of flour and sugar, but our refrigerator has only 1.5 gallons of milk and 1.5 dozen eggs. Since we don t want anyone to go without cake at our party, we need to know how many cakes we can make. [This is then a limiting reactant (reagent) problem.] 1cake 1pt milk 2 pt 1qt 4 qt 1gal ( 1.5 gal) = 12 cakes if all the milk is used up 1cake 2 eggs 12 eggs 1doz ( 1.5 doz) = 9 cakes if all the eggs are used up We then can only make nine cakes because we are limited by the number of eggs we have. If we make nine cakes, then how much milk will be left? 1pt 1cake ( 9 cakes) = 9 pts of milk used up We started with: 4 qt 1gal 2 pts 1qt ( 1.5 gal) = 12 pts of milk thus 12 minus 9 results in three pints of milk left over to drink with our cakes. The logic used to solve this fun problem is identical to that used in this section to solve chemical limiting reagent problems. Note that in the fun problem we used the logic of starting with the number of cakes made to determine the amount of excess milk left over. Another way to solve for the amount of excess milk would be to do the following:
6 12 eggs 1doz ( 1.5 doz eggs) = 18 eggs used 1pt 2 eggs ( 18 eggs used) = 9 pts of milk used 12 pts9pts = 3 pts of milk left over This second method is more in line with the way the author of the textbook solved the limiting reagent problem in Example It should be emphasized that one cannot assume that the reactant with the smallest mass is limiting. example, if grams of H 2 are reacted with 16 grams of O 2 to form water, which reactant is limiting? For 2H 2 + O 2 2H 2 O 1mol H 2 mol H O = g H 2 2 mol H 2 ( g H ) moles of H O if all the H are used 1mol O 2 mol H ) 16 2 = g O 2 1mol O 2 ( g O ) 2 2 1mole H O if all the O are used Thus, even though the mass of H 2 was less than the mass of O 2, the O 2 is the limiting reactant. Section 3.10 Reaction Yield As defined, it is possible that the % yield could be greater than 100%. This doesn t usually happen, but it could as a result of the following: an error in calculation measuring the product wrong contamination of the product (maybe with solvent) the reaction not following the scheme outlined (using the wrong chemical equation) Therefore, if there is no error in calculation, a percent yield greater than 100% gives valuable insight into what is actually happening in the system.
The Mole Concept. The Mole. Masses of molecules
The Mole Concept Ron Robertson r2 c:\files\courses\111020\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 informationFormulas, 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 informationAtomic 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 informationThe 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 informationChemical 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 informationPractice 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 informationPart 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 informationMass 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 informationChapter 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 informationIf 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 informationChemical Composition. Introductory Chemistry: A Foundation FOURTH EDITION. Atomic Masses. Atomic Masses. Atomic Masses. Chapter 8
Introductory Chemistry: A Foundation FOURTH EDITION by Steven S. Zumdahl University of Illinois Chemical Composition Chapter 8 1 2 Atomic Masses Balanced equation tells us the relative numbers of molecules
More informationPERIODIC 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 informationThe Mole Concept and Atoms
Copyright The McGrawHill Companies, Inc. Permission required for reproduction or display. Chapter 4 24 September 2013 Calculations and the Chemical Equation The Mole Concept and Atoms Atoms are exceedingly
More informationChapter 3 Chemical Reactions and Reaction Stoichiometry. 許富銀 ( Hsu FuYin)
Chapter 3 Chemical Reactions and Reaction Stoichiometry 許富銀 ( Hsu FuYin) 1 Stoichiometry The study of the numerical relationship between chemical quantities in a chemical reaction is called stoichiometry.
More informationCalculating 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 informationChapter 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 informationMole Relationships in Chemistry
Mole Relationships in Chemistry The Mole Concept and Atomic Masses The mole concept and molar mass is historically based on two laws from JosephLouis Proust in 1797 The Law of Definite Proportions This
More informationChapter 3. Stoichiometry: Ratios of Combination. Insert picture from First page of chapter. Copyright McGrawHill 2009 1
Chapter 3 Insert picture from First page of chapter Stoichiometry: Ratios of Combination Copyright McGrawHill 2009 1 3.1 Molecular and Formula Masses Molecular mass  (molecular weight) The mass in amu
More informationStoichiometry 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 informationAP 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 informationAT 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 informationChapter 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 informationLecture 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 1024 g How many 12 C atoms weigh 12 g?
More informationIB Chemistry 1 Mole. One atom of C12 has a mass of 12 amu. One mole of C12 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 carbon12 that were needed to make 12 g of carbon. 1 mole
More informationChem 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 informationWe know from the information given that we have an equal mass of each compound, but no real numbers to plug in and find moles. So what can we do?
How do we figure this out? We know that: 1) the number of oxygen atoms can be found by using Avogadro s number, if we know the moles of oxygen atoms; 2) the number of moles of oxygen atoms can be found
More informationChapter 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 information1. 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 1024 g B. We need a conversion to the macroscopic world. 1. How many hydrogen atoms are in 1.00 g of hydrogen?
More information4. 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 informationChemistry B11 Chapter 4 Chemical reactions
Chemistry B11 Chapter 4 Chemical reactions Chemical reactions are classified into five groups: A + B AB Synthesis reactions (Combination) H + O H O AB A + B Decomposition reactions (Analysis) NaCl Na +Cl
More informationElement 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 carbon12, 6p + + 6n 0 = atomic mass of 12.0 o For chlorine35, 17p + + 18n 0 = atomic mass of 35.0 atomic mass
More informationCHEMICAL 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 informationMoles and Chemical Reactions. Moles and Chemical Reactions. Molar mass = 2 x 12.011 + 6 x 1.008 + 1 x15.999 = 46.069 g/mol
We have used the mole concept to calculate mass relationships in chemical formulas Molar mass of ethanol (C 2 H 5 OH)? Molar mass = 2 x 12.011 + 6 x 1.008 + 1 x15.999 = 46.069 g/mol Mass percentage of
More informationChem 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 informationOrganic Chemistry Calculations
Organic Chemistry Calculations There are three basic units for measurement in the organic laboratory mass, volume, and number, measured in moles. Most of the other types of measurements are combinations
More informationOutline. 6.1 The Mole and Avogadro s Number. 6.2 Gram Mole Conversions. 6.3 Mole Relationships and Chemical Equations
Outline 6.1 The Mole and Avogadro s Number 6.2 Gram Mole Conversions 6.3 Mole Relationships and Chemical Equations 6.4 Mass Relationships and Chemical Equations 6.5 Limiting Reagent and Percent Yield Goals
More informationChemistry 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 informationOther 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 informationChapter 4. Chemical Composition. Chapter 4 Topics H 2 S. 4.1 Mole Quantities. The Mole Scale. Molar Mass The Mass of 1 Mole
Chapter 4 Chemical Composition Chapter 4 Topics 1. Mole Quantities 2. Moles, Masses, and Particles 3. Determining Empirical Formulas 4. Chemical Composition of Solutions Copyright The McGrawHill Companies,
More informationChemical 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 bookkeeping Chemical Equations Chemical equations: Describe proportions
More informationChapter 10 Chemical Quantities
Chapter 10 Chemical Quantities 101 The Mole: A Measurement 102 MoleMass and MoleVolume Relationships 103 Percent Composition and Chemical Formulas 1 Copyright Pearson Education, Inc, or its affiliates
More informationChapter 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 informationMatter. 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 informationChemical Equations and Calculations
Chemical Equations and Calculations A chemical equation is a shorthand way of indicating what is going on in a chemical reaction. We could do it the long way Two molecules of Hydrogen gas react with one
More informationChapter 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 informationTHE MOLE / COUNTING IN CHEMISTRY
1 THE MOLE / COUNTING IN CHEMISTRY ***A mole is 6.0 x 10 items.*** 1 mole = 6.0 x 10 items 1 mole = 60, 00, 000, 000, 000, 000, 000, 000 items Analogy #1 1 dozen = 1 items 18 eggs = 1.5 dz.  to convert
More informationUseful 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 1024 grams = mass of a proton
More informationFormulas, 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 informationStoichiometry: Calculations with Chemical Equations
Stoichiometry: Calculations with Chemical Equations Objectives Use chemical equations to predict amount of product from given reactants Determine percentage yield Determine limiting reactant Working with
More informationGeorgia Institute of Technology CHEM 1310 Fall Semester 2009 Recitation Assignment! Fundamental Principles and Terminology
The Fundamentals and Stoichiometry Recitation Worksheet Week of 25 August 2008. Fundamental Principles and Terminology Avogadro s Number: Used to represent the amount of a given atom as a basis for comparison
More informationSample Problem: STOICHIOMETRY and percent yield calculations. How much H 2 O will be formed if 454 g of. decomposes? NH 4 NO 3 N 2 O + 2 H 2 O
STOICHIOMETRY and percent yield calculations 1 Steps for solving Stoichiometric Problems 2 Step 1 Write the balanced equation for the reaction. Step 2 Identify your known and unknown quantities. Step 3
More informationChapter 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 informationMolecular Formula: Example
Molecular Formula: Example A compound is found to contain 85.63% C and 14.37% H by mass. In another experiment its molar mass is found to be 56.1 g/mol. What is its molecular formula? 1 CHAPTER 3 Chemical
More informationSubscripts 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 informationChapter 6: Chemical Composition
C h e m i s t r y 1 2 C h 6 : C h e m i c a l C o m p o s i t i o n P a g e 1 Chapter 6: Chemical Composition Bonus: 17, 21, 31, 39, 43, 47, 55, 61, 63, 69, 71, 77, 81, 85, 91, 95, 97, 99 Check the deadlines
More informationChem 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 informationCONSERVATION OF MASS During a chemical reaction, matter is neither created nor destroyed.  i. e. the number of atoms of each element remains constant
1 CHEMICAL REACTINS Example: Hydrogen + xygen Water H + H + +  Note there is not enough hydrogen to react with oxygen  It is necessary to balance equation. reactants products + H + H (balanced equation)
More informationChapter 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 informationThe 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 informationIntroduction to Chemistry
1 Copyright ç 1996 Richard Hochstim. All rights reserved. Terms of use. Introduction to Chemistry In Chemistry the word weight is commonly used in place of the more proper term mass. 1.1 Atoms, Ions, and
More informationPerforming Calculatons
Performing Calculatons There are three basic units for measurement in the organic laboratory mass, volume, and number, measured in moles. Most of the other types of measurements are combinations of them,
More informationThe 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 informationChapter 7: Stoichiometry  Mass Relations in Chemical Reactions
Chapter 7: Stoichiometry  Mass Relations in Chemical Reactions How do we balance chemical equations? How can we used balanced chemical equations to relate the quantities of substances consumed and produced
More informationThe Mole. S We are familiar with using a specific term to represent a number of items in a group.
Unit 5 The Mole S The Mole S We are familiar with using a specific term to represent a number of items in a group. S 1 dozen = 12 units of something S 1 case of Cokes = 24 Cokes S In chemistry we use the
More informationEMPIRICAL 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 informationChapter 1 The Atomic Nature of Matter: Selected Answersc for Practice Exam.
Chapter 1 The Atomic Nature of Matter: Selected Answersc for Practice Exam. MULTIPLE CHOICE 50. 5.80 g of dioxane (C 4 H 8 O 2 ) is how many moles of dioxane? 0.0658 mol 0.0707 mol 0.0725 mol d. 0.0804
More informationIntroductory Chemistry Fourth Edition Nivaldo J. Tro
Introductory Chemistry Fourth Edition Nivaldo J. Tro Chapter 6 Chemical Composition Dr. Sylvia Esjornson Southwestern Oklahoma State University Weatherford, OK 6.1 How Much Sodium? Sodium is an important
More informationHow 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 informationChemical Reactions. Chemistry 100. Bettelheim, Brown, Campbell & Farrell. Introduction to General, Organic and Biochemistry Chapter 4
Chemistry 100 Bettelheim, Brown, Campbell & Farrell Ninth Edition Introduction to General, Organic and Biochemistry Chapter 4 Chemical Reactions Chemical Reactions In a chemical reaction, one set of chemical
More informationStoichiometry. Types of Problems. Stoichiometry. Chemistry 1010 Review Tutorial 4/9/2013. Stoichiometry and Lewis Structures
Stoichiometry Chemistry 1010 Review Tutorial Stoichiometry and Lewis Structures April 9 th, 2013 Stoichiometry Stoichiometry involves MOLES Elements/compounds can only be compared side by side using moles
More informationStoichiometry. 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 catbon12
More informationCH3 Stoichiometry. The violent chemical reaction of bromine and phosphorus. P.76
CH3 Stoichiometry The violent chemical reaction of bromine and phosphorus. P.76 Contents 3.1 Counting by Weighing 3.2 Atomic Masses 3.3 The Mole 3.4 Molar Mass 3.5 Percent Composition of Compounds 3.6
More informationCHAPTER 3 Calculations with Chemical Formulas and Equations. atoms in a FORMULA UNIT
CHAPTER 3 Calculations with Chemical Formulas and Equations MOLECULAR WEIGHT (M. W.) Sum of the Atomic Weights of all atoms in a MOLECULE of a substance. FORMULA WEIGHT (F. W.) Sum of the atomic Weights
More informationChem 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 information2 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 informationCalculations with Chemical Formulas and Equations
Chapter 3 Calculations with Chemical Formulas and Equations Concept Check 3.1 You have 1.5 moles of tricycles. a. How many moles of seats do you have? b. How many moles of tires do you have? c. How could
More informationChapter 3: ex. P2O5 molecular mass = 2(30.97 amu) + 5(16.00 amu) = amu
Molecular Mass and Formula Mass for molecular compounds: the molecular mass is the mass (in amu) of one molecule of the compound molecular mass = atomic masses of elements present Chapter 3: ex. P2O5 molecular
More informationINTRODUCTORY CHEMISTRY Concepts and Critical Thinking
INTRODUCTORY CHEMISTRY Concepts and Critical Thinking Sixth Edition by Charles H. Corwin Chapter 9 The Mole Concept by Christopher Hamaker 2011 Pearson Education, Inc. Chapter 9 1 Avogadro s Number Avogadro
More informationLecture 5 Outline. Derived from the Greek stoicheion ( element ) and metron ( measure )
Lecture 5 Outline 5.1 Stoichiometry,, the mole etc. 5.2 Chemical Equations 5.3 Molarity 5.4 Limiting reagents and yields 5.5 Reaction enthalpies and Gibbs free energy 5.6 Catalyst Lecture 5 Stoichiometry
More informationChemical Equations & Stoichiometry
Chemical Equations & Stoichiometry Chapter Goals Balance equations for simple chemical reactions. Perform stoichiometry calculations using balanced chemical equations. Understand the meaning of the term
More informationCh. 10 The Mole I. Molar Conversions
Ch. 10 The Mole I. Molar Conversions I II III IV A. What is the Mole? A counting number (like a dozen) Avogadro s number (N A ) 1 mole = 6.022 10 23 representative particles B. Mole/Particle Conversions
More informationChapter 3. Stoichiometry of Formulas and Equations
Chapter 3 Stoichiometry of Formulas and Equations Chapter 3 Outline: Mole  Mass Relationships in Chemical Systems 3.1 The Mole 3.2 Determining the Formula of an Unknown Compound 3.3 Writing and Balancing
More informationExploring Gas Laws. Chapter 12. Solutions for Practice Problems. Student Textbook page 477
Chapter 12 Exploring Gas Laws Solutions for Practice Problems Student Textbook page 477 1. Problem At 19 C and 100 kpa, 0.021 mol of oxygen gas, O 2(g), occupy a volume of 0.50 L. What is the molar volume
More informationMOLAR 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 informationMoles. Balanced chemical equations Molar ratios Mass Composition Empirical and Molecular Mass Predicting Quantities Equations
Moles Balanced chemical equations Molar ratios Mass Composition Empirical and Molecular Mass Predicting Quantities Equations Micro World atoms & molecules Macro World grams Atomic mass is the mass of an
More informationBalanced Chemical Reaction Equations
Activity 5 Balanced Chemical Reaction Equations Why? Chemical reaction equations are fundamental tools for communicating how chemical compounds are synthesized and changed. Representing a chemical reaction
More informationChapter 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 informationMOLES, 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 informationMolecular Masses Recall: periodic table gives us the average mass (u) of an atom of a specified element
Chapter 3 (Hill/Petrucci/McCreary/Perry Stoichiometry: Chemical Calculations This chapter deals with quantitative relationships in compounds and between compounds in chemical reactions. These quantitative
More informationMole  Mass Relationships in Chemical Systems
Chapter 3: Stoichiometry 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 Equations 3.4 Calculating the Amounts
More informationChapter 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 informationChemical formulae are used as shorthand to indicate how many atoms of one element combine with another element to form a compound.
29 Chemical Formulae Chemical formulae are used as shorthand to indicate how many atoms of one element combine with another element to form a compound. C 2 H 6, 2 atoms of carbon combine with 6 atoms of
More informationTOPIC 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 informationSimple vs. True Calculating Empirical and Molecular Formulas
17 Calculating Empirical and Molecular Formulas OBJECTIVE Students will learn to calculate empirical and molecular formulas and practice applying logical problemsolving skills. LEVEL Chemistry NATIONAL
More informationThe 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 informationFormula Stoichiometry. Text pages
Formula Stoichiometry Text pages 237250 Formula Mass Review Write a chemical formula for the compound. H 2 CO 3 Look up the average atomic mass for each of the elements. H = 1.008 C= 12.01 O = 16.00 Multiply
More informationTuesday, October 23rd. Review Quiz Finish Chapter 6, Begin Chapter 7 Group Assignment
Tuesday, October 23rd Review Quiz Finish Chapter 6, Begin Chapter 7 Group Assignment 1 Review 2 Naming Ionic Compounds  When a metal is bonded to a nonmetal: 1. Name the metal. 2. Name the anion, use
More information10.3 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 MoleMass and MoleVolume Relationships 103 Percent Composition and Chemical Formulas 1 CHEMISTRY & YOU What does the percent composition
More informationSTOICHIOMETRY.  the study of the quantitative aspects of chemical
STOICHIOMETRY  the study of the quantitative aspects of chemical GENERAL PLAN FOR STOICHIOMETRY Mass reactant Mass product Moles reactant Stoichiometric factor Moles product STOICHIOMETRY It rests on
More informationMASS RELATIONSHIPS IN CHEMICAL REACTIONS
MASS RELATIONSHIPS IN CHEMICAL REACTIONS 1. The mole, Avogadro s number and molar mass of an element. Molecular mass (molecular weight) 3. Percent composition of compounds 4. Empirical and Molecular formulas
More information