To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video
Save this PDF as:

Size: px
Start display at page:

## Transcription

2 QUESTION Suppose you work in a hardware store and a customer wants to purchase 500 nails. If the average mass of a nail is 20 grams, how many kilograms of nails would you weigh out? kg kg kg kg Copyright Cengage Learning. All rights reserved. 8 2

3 ANSWER Choice #1 is the correct answer. This problem illustrates the concept of counting by weighing. Rather than laboriously counting out 500 nails we use the average mass of a nail to compute the mass of 500 nails and simply weigh out the correct mass. 20 g 1 kg 500 nails 10 kg 1 nail 1000 g Copyright Cengage Learning. All rights reserved. 8 3

4 QUESTION A pile of marbles weigh g. 10 marbles weigh g. How many marbles are in the pile? Copyright Cengage Learning. All rights reserved. 8 4

5 ANSWER Choice #3 is the correct answer. Avg. Mass of 1 Marble = g 10 marbles = 3.76 g / marble g = 105 marbles 3.76 g Copyright Cengage Learning. All rights reserved. 8 5

6 QUESTION Atomic masses on the periodic table are not reported as whole numbers. What is the chief reason for this? 1. Atoms are so small that even modern techniques have a limited accuracy, which keeps the value from being a whole number. 2. Atomic mass scales are based on hydrogen 1.01, and since this atom does not have a whole number mass the comparisons will not be able to have whole number masses also. 3. Isotopic abundance is averaged to provide the mass of atoms. 4. Atomic mass is based on a variable scale. Copyright Cengage Learning. All rights reserved. 8 6

7 ANSWER Choice #3 properly explains that the masses of elements are based on the weighted average of the isotopes for each element. Copyright Cengage Learning. All rights reserved. 8 7

8 QUESTION Since it is extremely difficult to see atoms without elaborate equipment, chemists use the atomic mass scale to determine the number of atoms in a sample. For example, calculate the number of aluminum atoms in a piece of aluminum foil that weighs amu x x x x Copyright Cengage Learning. All rights reserved. 8 8

10 QUESTION Diamond is an allotrope of carbon. If 1.0 carat has a mass of 0.20 grams, how many carbon atoms are in a 3.0 carat diamond? x x x x Copyright Cengage Learning. All rights reserved. 8 10

11 ANSWER Choice #4 correctly gives the atomic make up of the 3.0 carat diamond g C 1 amu C 1 atom C 3.0 c c g C amu C atoms C Copyright Cengage Learning. All rights reserved. 8 11

12 QUESTION Calculate the number of iron atoms in a 4.48 mole sample of iron Copyright Cengage Learning. All rights reserved. 8 12

14 QUESTION The metal gallium (Ga) has most of the properties you would expect in a metal, but it is so soft it will melt in your hand. If you had 20.0 grams of solid gallium in your palm and watched it turn into liquid, how many moles of liquid gallium would you soon have? moles moles moles moles Copyright Cengage Learning. All rights reserved. 8 14

15 ANSWER Choice #2 represents the mole equivalent for 20.0 grams of gallium. 1 mole Ga 20.0 g Ga moles Ga 69.7 g Ga Copyright Cengage Learning. All rights reserved. 8 15

16 QUESTION Which of the following is closest to the average mass of one atom of copper? g g g x g Copyright Cengage Learning. All rights reserved. 8 16

17 ANSWER Choice #4 is the correct answer. The mass of one atom of copper is going to be extremely small, so only Choice #4 makes sense. The calculated solution is: 1 mol Cu g Cu 22 1 Cu atom = g Cu Cu atoms 1 mol Cu Copyright Cengage Learning. All rights reserved. 8 17

18 QUESTION A sample of grams of Al has the same number of atoms as grams of Au g g g g Copyright Cengage Learning. All rights reserved. 8 18

19 ANSWER Choice #3 gives the mass of 1.0 mole of gold. The g of Al represents 1.0 mole of Al. Thus both samples contain Avogadro s number, atoms. Copyright Cengage Learning. All rights reserved. 8 19

20 QUESTION Which silver ring would be worth more? 1. A ring that weighs 10.0 grams. 2. A ring that consists of atoms of Ag. Copyright Cengage Learning. All rights reserved. 8 20

21 ANSWER Choice #1 is the correct answer. The ring that weighs 10.0 g would be worth more. We can tell by using dimensional analysis to figure out how much the atoms of Ag would weigh: 22 1 mole Ag g Ag atoms Ag 1.8 g Ag x 10 atoms Ag 1 mole Ag Copyright Cengage Learning. All rights reserved. 8 21

22 QUESTION Which of the following g samples contains the greatest number of atoms? 1. Magnesium 2. Zinc 3. Silver Copyright Cengage Learning. All rights reserved. 8 22

23 ANSWER Choice #1 is the correct answer. Magnesium has the smallest average atomic mass (24.31 amu). Since magnesium is lighter than zinc and silver, it will take more atoms to reach g. Copyright Cengage Learning. All rights reserved. 8 23

24 QUESTION You have two beakers on your lab table. Beaker #1 contains g of sulfur (S) and Beaker #2 contains g of arsenic (As). Which beaker contains the greatest number of atoms? Choose the best answer. 1. Beaker #1 because one sulfur atom weighs less than one arsenic atom so you need more of the sulfur atoms to fill the beaker. 2. Beaker #2 because arsenic has a greater mass than sulfur. 3. Beaker #2 because it contains more moles of arsenic atoms versus the number of moles of sulfur atoms in Beaker #1. 4. Beakers #1 and #2 contain the same number of atoms because there is one mole in each. Copyright Cengage Learning. All rights reserved. 8 24

26 QUESTION One mole of carbon is equivalent to atomic mass units. 2. the same mass of atoms that are contained in one mole of calcium. 3. the same number of atoms that are contained in one mole of calcium grams of carbon. Copyright Cengage Learning. All rights reserved. 8 26

31 ANSWER Choice #3 is the correct answer. The formula for ammonium phosphate is (NH 4 ) 3 PO 4. Therefore the molar mass is: 3(14.01) + 12(1.008) (16.00) = g/mol. Copyright Cengage Learning. All rights reserved. 8 31

32 QUESTION Consider equal mole samples of N 2 O, Al(NO 3 ) 3, and KCN. Rank these from least to most number of nitrogen atoms in each sample. 1. KCN, Al(NO 3 ) 3, N 2 O 2. Al(NO 3 ) 3, N 2 O, KCN 3. KCN, N 2 O, Al(NO 3 ) 3 4. Al(NO 3 ) 3, KCN, N 2 O Copyright Cengage Learning. All rights reserved. 8 32

33 ANSWER Choice #3 is the correct answer. Assume you have one mole of each sample. This means you have 1 mole of N in KCN, 2 moles of N in N 2 O and 3 moles of N in Al(NO 3 ) 3. Moles are directly related through Avogadro s number. Copyright Cengage Learning. All rights reserved. 8 33

34 QUESTION You have 27.0 g of an unknown substance A and 75.0 g of chlorine gas. Substance A contains 1.5 times as many molecules as the chlorine gas. What is the identity of A? 1. HClO 2. NO 2 3. BF 3 4. NH 3 Copyright Cengage Learning. All rights reserved. 8 34

35 ANSWER Choice #4 is the correct answer. To identify A, you need to know the molar mass (# grams/# moles). The number of grams of A is already given. To find the moles of A: 1 mol Cl 1.5 mol A g Cl = 1.6 mol A g Cl 1 mol Cl 2 2 Therefore the molar mass of A is 17 g/mol (27.0 g/1.6 mol), which is NH 3. Copyright Cengage Learning. All rights reserved. 8 35

36 QUESTION How many grams of fluorine are contained in one molecule of boron trifluoride? g g g g Copyright Cengage Learning. All rights reserved. 8 36

37 ANSWER Choice #2 is the correct answer. 1 molecule BF 3 23 = g F 3 atoms F 1 mol F g F 23 1 molecule BF atoms F 1 mol F 3 Copyright Cengage Learning. All rights reserved. 8 37

38 QUESTION Morphine, derived from opium plants, has the potential for use and abuse. It s formula is C 17 H 19 NO 3. What percent, by mass, is the carbon in this compound? % % % % Copyright Cengage Learning. All rights reserved. 8 38

39 ANSWER Choice #4 is correct. First determine the molar mass of the compound, then divide that into the total mass of carbon present. Finally multiply that by 100 to convert from a fraction into a percentage = = 71.6% C Copyright Cengage Learning. All rights reserved. 8 39

40 QUESTION What is the mass percent of potassium in potassium nitride? % % % % Copyright Cengage Learning. All rights reserved. 8 40

42 QUESTION What is the percent mass of phosphorus in calcium phosphide? % % % % Copyright Cengage Learning. All rights reserved. 8 42

44 QUESTION A gas consisting of 50.0% sulfur and 50.0% oxygen by mass has what empirical formula? 1. SO 2. SO 2 3. S 2 O 4. SO 4 Copyright Cengage Learning. All rights reserved. 8 44

45 ANSWER Choice #2 is the smallest whole number ratio of the atoms that make up this compound. When presented with % composition data, we start out by assuming we have 100 g of that compound so that the % s are masses in grams. We then convert the masses into moles using atomic masses: 1 mole S 50.0 g S 1.56 mole S g S 1 mole O 50.0 g O 3.13 mole O g O We then divide by the smallest # of moles: 3.13/1.56 = 2 Therefore # moles O/# moles S = 2/1 SO 2 Copyright Cengage Learning. All rights reserved. 8 45

46 QUESTION A hydrocarbon (binary compound containing carbon and hydrogen) has a percent composition of 92% carbon and 8% hydrogen and a molar mass of about 26 g/mol. Determine the molecular formula of this compound. 1. CH 4 2. C 2 H 4 3. C 2 H 2 4. CH 2 Copyright Cengage Learning. All rights reserved. 8 46

47 ANSWER Choice #3 is the only formula listed with a molar mass of 26 g/mol. To see how the formula is worked out, we convert the % s to grams and divide by atomic masses: 1 mole C 92 g C 7.7 mole C g C 1 mole H 8 g H x 8 mole H g H 7.7 rounds off to 8 so C/H is 1/1 in the compound. The empirical formula is CH, but this has a molecular weight of /13 = 2, so we multiply the formula CH by 2 to give C 2 H 2. Copyright Cengage Learning. All rights reserved. 8 47

48 QUESTION Vinegar contains carbon, hydrogen, and oxygen with percent masses of 40.01% C and 6.70% H, respectively. If the molar mass of vinegar is about 60 g/mol, what is its molecular formula? 1. CH 2 O 2. C 3 H 8 O 3. C 2 H 20 O 4. C 2 H 4 O 2 Copyright Cengage Learning. All rights reserved. 8 48

49 ANSWER Choice #4 is the correct answer. The empirical formula is CH 2 O with a molar mass of about 30 g/mol. 60/30 = 2, so we multiply the formula CH 2 O by 2 to get C 2 H 4 O 2. Copyright Cengage Learning. All rights reserved. 8 49

50 QUESTION A compound consists of silicon and 8.23% by mass of hydrogen. The molar mass of the compound is approximately 122 g/mol. What is the molecular formula of this compound? 1. Si 4 H SiH 2 3. SiH 3 4. Si 2 H 5 Copyright Cengage Learning. All rights reserved. 8 50

51 ANSWER Choice #1 is the correct answer. The empirical formula is Si 2 H 5 with a molar mass of about 61 g/mol. 122/61 = 2, so we multiply the formula Si 2 H 5 by 2 to get Si 4 H 10. Copyright Cengage Learning. All rights reserved. 8 51

### 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

### Unit 2. Molar Mass Worksheet

Unit 2 Molar Mass Worksheet Calculate the molar masses of the following chemicals: 1) Cl 2 8) UF 6 2) KOH 9) SO 2 3) BeCl 2 10) H 3 PO 4 4) FeCl 3 11) (NH 4 ) 2 SO 4 5) BF 3 12) CH 3 COOH 6) CCl 2 F 2

### 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

### 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.

### 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

### 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

### TUTORIAL 5-1 HELP. Mass of sodium = 23.0 g/mol x 3 mol = 69.0 g of sodium. Percent mass of sodium = 69.0 g x 100% = 42.

TUTORIAL 5-1 HELP ANSWER TO QUESTION 1 ON TUTORIAL 5-1: Question 1. Find the percent composition by mass of sodium phosphate, Na 3 PO 4. Step 1: Find the molar mass of Na 3 PO 4 (The mass of one mole of

### 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

### 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

### SYMBOLS, FORMULAS AND MOLAR MASSES

SYMBOLS, FORMULAS AND MOLAR MASSES OBJECTIVES 1. To correctly write and interpret chemical formulas 2. To calculate molecular weights from chemical formulas 3. To calculate moles from grams using chemical

### Ch. 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

### Molar Mass Worksheet Answer Key

Molar Mass Worksheet Answer Key Calculate the molar masses of the following chemicals: 1) Cl 2 71 g/mol 2) KOH 56.1 g/mol 3) BeCl 2 80 g/mol 4) FeCl 3 162.3 g/mol 5) BF 3 67.8 g/mol 6) CCl 2 F 2 121 g/mol

### 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

### 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

### 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,

### Moles, Molecules, and Grams Worksheet Answer Key

Moles, Molecules, and Grams Worksheet Answer Key 1) How many are there in 24 grams of FeF 3? 1.28 x 10 23 2) How many are there in 450 grams of Na 2 SO 4? 1.91 x 10 24 3) How many grams are there in 2.3

### 2 The Structure of Atoms

CHAPTER 4 2 The Structure of Atoms SECTION Atoms KEY IDEAS As you read this section, keep these questions in mind: What do atoms of the same element have in common? What are isotopes? How is an element

### 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

### Chapter 8 Chemical Quantities

Chapter 8 Chemical Quantities Introductory Info The atomic masses of the elements on the periodic table are in the units. These measurements are based on the mass of the standard isotope of the element,

### Chapter 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 McGraw-Hill Companies,

### 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

### The Mole Concept and Atoms

Copyright The McGraw-Hill 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

### 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

### Chapter 7 Part II: Chemical Formulas and Equations. Mr. Chumbley Chemistry 1-2

Chapter 7 Part II: Chemical Formulas and Equations Mr. Chumbley Chemistry 1-2 SECTION 3: USING CHEMICAL FORMULAS Molecules and Formula Unit We have not yet discussed the different ways in which chemical

### 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

### MOLECULAR MASS AND FORMULA MASS

1 MOLECULAR MASS AND FORMULA MASS Molecular mass = sum of the atomic weights of all atoms in the molecule. Formula mass = sum of the atomic weights of all atoms in the formula unit. 2 MOLECULAR MASS AND

### Ch. 6 Chemical Composition and Stoichiometry

Ch. 6 Chemical Composition and Stoichiometry The Mole Concept [6.2, 6.3] Conversions between g mol atoms [6.3, 6.4, 6.5] Mass Percent [6.6, 6.7] Empirical and Molecular Formula [6.8, 6.9] Bring your calculators!

### Chapter 4 Chemical Composition

Chapter 4 Chemical Composition 4.1 (a) mole; (b) Avogadro s number; (c) empirical formula; (d) solute; (e) molarity; (f) concentrated solution 4. (a) molar mass; (b) percent composition by mass; (c) solvent;

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

### We 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

### Name Block THE MOLE. Who s Counting Lab. Mole Notes. Mole Calculations. Mixed Mole Conversions. % Comp, Emp, and Molecular Calcuations

Name Block THE MOLE Who s Counting Lab Mole Notes Mole Calculations Mixed Mole Conversions % Comp, Emp, and Molecular Calcuations Mole Notes, Part 1 1. The Mole is just a long word for changing units

### Percent Composition - Formulas

Percent Composition - Formulas This program demonstrates how to find percentage composition as well as empirical and molecular formulas from that data. Please read each section carefully. You might wish

### 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.

### 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

### Formula Stoichiometry. Text pages

Formula Stoichiometry Text pages 237-250 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

### Section 6.6: The Composition of Unknown Compounds

Section 6.6: The Composition of Unknown Compounds Tutorial 1 Practice, page 286 1. Given: = 4.60 g ; m N = 1.40 g Required: percentage of each element: % N; % O Step 1. Use the percentage formula to calculate

### Chapter 3 Mass Relationships in Chemical Reactions

Chapter 3 Mass Relationships in Chemical Reactions Student: 1. An atom of bromine has a mass about four times greater than that of an atom of neon. Which choice makes the correct comparison of the relative

### Chemical Quantities: The Mole Chapter 7 Assignment & Problem Set

Chemical Quantities: The Mole Name Warm-Ups (Show your work for credit) Date 1. Date 2. Date 3. Date 4. Date 5. Date 6. Date 7. Date 8. Chemical Quantities: The Mole 2 Study Guide: Things You Must Know

### Chapter 5. Quantities in Chemistry

Chapter 5 Quantities in Chemistry REMEMBER: You are required to use dimensional analysis whenever possible, which is almost all of the time in chemistry! If you choose not to use dimensional analysis,

### Chapter 3 Stoichiometry: Calculations with Chemical Formulas and Equations

CHE11 Chapter Chapter Stoichiometry: Calculations with Chemical Formulas and Equations 1. When the following equation is balanced, the coefficients are. NH (g) + O (g) NO (g) + H O (g) (a). 1, 1, 1, 1

### SCH 4C1 Unit 2 Problem Set Questions taken from Frank Mustoe et all, "Chemistry 11", McGraw-Hill Ryerson, 2001

SCH 4C1 Unit 2 Problem Set Questions taken from Frank Mustoe et all, "Chemistry 11", McGraw-Hill Ryerson, 2001 1. A small pin contains 0.0178 mol of iron. How many atoms of iron are in the pin? 2. A sample

### Problem Solving. Empirical Formulas

Skills Worksheet Problem Solving 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

### 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

### Chapter 3 Mass Relations in Chemistry; Stoichiometry

Chapter 3 Mass Relations in Chemistry; Stoichiometry MULTIPLE CHOICE 1. An atomic mass unit (amu) is defined as a. 1.60 10-19 C. b. the mass of 1 mole of hydrogen-s. c. the mass of 1 hydrogen-. d. the

### Suggested Resources Textbook: Chapter 6 (6.3, 6.4, 6.5 & 6.6)

The Mole Big Picture Ideas: 1. The mole is a unit of count. 2. Using conversion factors, one can convert between mass, moles, particles and volume for a given substance. 3. Empirical data including percent

### B. Elements: We cannot determine how many electrons are lost for the elements b/c their in their valence electrons can change.

Unit 6 Notepack: Chapters 9 &10 Chemical Quantities 9.1 Naming Ions NAME Period: A. ions: Ions made of single. B. Elements: There is a pattern in predicting how many electrons are lost and gained for the

### 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

### CHAPTER 8: CHEMICAL COMPOSITION

CHAPTER 8: CHEMICAL COMPOSITION Active Learning: 1-4, 6-8, 12, 18-25; End-of-Chapter Problems: 3-4, 9-82, 84-85, 87-92, 94-104, 107-109, 111, 113, 119, 125-126 8.2 ATOMIC MASSES: COUNTING ATOMS BY WEIGHING

### CHAPTER 3 STOICHIOMETRY OF FORMULAS AND EQUATIONS

CHAPTER 3 STOICHIOMETRY OF FORMULAS AND EQUATIONS FOLLOW UP PROBLEMS 3.1A Plan: The mass of carbon must be changed from mg to g. The molar mass of carbon can then be used to determine the number of moles.

### MODERN CHEMISTRY. 8. What is the formula for aluminum sulfate? 9. What is the formula for barium hydroxide?

MODERN CHEMISTRY Date Name Period Multiple Choice - Identify the choice that best completes the statement or answers the question. Use answer-key worksheet (Page 6) to key in answers to questions. 1. A

### 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

### AP Chemistry Prep - Summer Assignment 2013

AP Chemistry Prep - Summer Assignment 2013 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. Which value has only 4 significant digits? a. 6.930 c. 8450

### 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

### 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

### = 16.00 amu. = 39.10 amu

Using Chemical Formulas Objective 1: Calculate the formula mass or molar mass of any given compound. The Formula Mass of any molecule, formula unit, or ion is the sum of the average atomic masses of all

### CHM-101-A Exam 2 Version 1 October 10, 2006

CHM-101-A Exam 2 Version 1 1. Which of the following statements is incorrect? A. SF 4 has ¼ as many sulfur atoms as fluorine atoms. B. Ca(NO 3 ) 2 has six times as many oxygen atoms as calcium ions. C.

### 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

### 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

### Chapter 6 Chemical Composition

Chapter 6 Chemical Composition 1. 100 washers 0.110 g 1 washer = 11.0 g (assuming 100 washers is exact) 100. g 1 washer 0.110 g = 909 washers 2. 500. g 1 cork 1.63 g = 306.7 = 307 corks 500. g 1 stopper

### Chapter 4 Chemical Composition. Moles of Various Elements and Compounds Figure 4.8

Chapter 4 Chemical Composition Mole Quantities Moles, Masses, and Particles Determining Empirical and Molecular Formulas Chemical Composition of Solutions 4-1 Copyright The McGraw-Hill Companies, Inc.

### Gen Chem I Exam 1 Review (Chapters 1 & 2)

Gen Chem I Exam 1 Review (Chapters 1 & 2) 1 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. All of the following are properties of antimony. Which one

### 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

### CHEM J-2 June /01(a) What is the molarity of the solution formed when 0.50 g of aluminium fluoride is dissolved in ml of water?

CHEM1001 2014-J-2 June 2014 22/01(a) What is the molarity of the solution formed when 0.50 g of aluminium fluoride is dissolved in 800.0 ml of water? 2 The molar mass of AlF 3 is: molar mass = (26.98 (Al)

### MASS RELATIONS IN CHEMISTRY; STOICHIOMETRY

MASS RELATIONS IN CHEMISTRY; STOICHIOMETRY [MH5; Ch. 3] Each element has its own unique mass. The mass of each element is found on the Periodic Table under the chemical symbol for the element (it is usually

### 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

### Chemical 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

### The Mole Notes. There are many ways to or measure things. In Chemistry we also have special ways to count and measure things, one of which is the.

The Mole Notes I. Introduction There are many ways to or measure things. In Chemistry we also have special ways to count and measure things, one of which is the. A. The Mole (mol) Recall that atoms of

### What s in a Mole? Molar Mass

LESSON 10 What s in a Mole? Molar Mass OVERVIEW Key Ideas Lesson Type Lab: Groups of 4 Chemists compare moles of substances rather than masses because moles are a way of counting atoms. When considering

### Monday January 23rd CHAPTER 10

Monday January 23rd BELL WORK: In what quantity do eggs usually come in at the store? How many gloves do you usually buy at one time? What is a group of pencils that you might buy at the store called?

### 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,

### Chemical bonding is the true difference between compounds and mixtures. Atomic elements:

Chapter 3 - Molecules, compounds, and chemical equations Elements and compounds Chemical bonding is the true difference between compounds and mixtures Atomic elements: Ionic bond: attraction of oppositely

### Calculation of Molar Masses. Molar Mass. Solutions. Solutions

Molar Mass Molar mass = Mass in grams of one mole of any element, numerically equal to its atomic weight Molar mass of molecules can be determined from the chemical formula and molar masses of elements

### 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

### Multiple Choice Identify the letter of the choice that best completes the statement or answers the question.

Introduction to Chemistry Exam 2 Practice Problems 1 Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. 1.Atoms consist principally of what three

### 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

### 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

### INTRODUCTORY 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

### The Mole IT IS JUST A STANDARD NUMBER OF ATOMS/MOLECULES

The Mole S 6.02 X 10 23 IT IS JUST A STANDARD NUMBER OF ATOMS/MOLECULES Relative Masses To understand relative scales, let s s ignore electrons and compare atoms by total number of nuclear particles. Hydrogen,

### 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

### 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?

### EXPERIMENT 12: Empirical Formula of a Compound

EXPERIMENT 12: Empirical Formula of a Compound INTRODUCTION Chemical formulas indicate the composition of compounds. A formula that gives only the simplest ratio of the relative number of atoms in a compound

### 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

### Chapter 6 Notes. Chemical Composition

Chapter 6 Notes Chemical Composition Section 6.1: Counting By Weighing We can weigh a large number of the objects and find the average mass. Once we know the average mass we can equate that to any number

### 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.

### The Mole. Chapter 2. Solutions for Practice Problems

Chapter 2 The Mole 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 contains the full set of

### Unit 2: Quantities in Chemistry

Mass, Moles, & Molar Mass Relative quantities of isotopes in a natural occurring element (%) E.g. Carbon has 2 isotopes C-12 and C-13. Of Carbon s two isotopes, there is 98.9% C-12 and 11.1% C-13. Find

### 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?

### 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?

### Georgia 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

### 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

### 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

### Periodic Table, Valency and Formula

Periodic Table, Valency and Formula Origins of the Periodic Table Mendelѐѐv in 1869 proposed that a relationship existed between the chemical properties of elements and their atomic masses. He noticed

### Chapter 4. The Mole Concept

Chapter 4. The Mole Concept Introduction If you were to take one volume (Eg. 1cm 3 ) of every element, weigh them and rank them according to their weights you would discover that they followed the periodic

### 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

### A dozen. Molar Mass. Mass of atoms

A dozen Molar Mass Science 10 is a number of objects. A dozen eggs, a dozen cars, and a dozen people are all 12 objects. But a dozen cars has a much greater mass than a dozen eggs because the mass of each

CHAPTER 222 Galaxies have hundreds of billions of stars. The universe may have as many as sextillion stars that s 1000 000 000 000 000 000 000 (or 1 10 21 ) stars. Such a number is called astronomical

### Solution. Practice Exercise. Concept Exercise

Example Exercise 9.1 Atomic Mass and Avogadro s Number Refer to the atomic masses in the periodic table inside the front cover of this textbook. State the mass of Avogadro s number of atoms for each of

### 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