1 chapter 5 chemical quantities and reactions 5.1 the mole copyright 2009 by pearson education, inc

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Chapter 5 Chemical Quantities and Reactions

5.1The Mole

Copyright © 2009 by Pearson Education, Inc.

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Collection Terms

A collection term statesa specific number of items.

• 1 dozen donuts = 12 donuts

• 1 ream of paper = 500 sheets

• 1 case = 24 cans


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A mole is a collection that contains

• the same number of particles as there are carbon atoms in 12.0 g of carbon.

• 6.02 x 1023 atoms of an element (Avogadro’s number).

1 mole element Number of Atoms1 mole C = 6.02 x 1023 C atoms1 mole Na = 6.02 x 1023 Na atoms1 mole Au = 6.02 x 1023 Au atoms

A Mole of Atoms

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A mole • of a covalent compound has Avogadro’s number of

molecules.1 mole CO2 = 6.02 x 1023 CO2 molecules1 mole H2O = 6.02 x 1023 H2O molecules

• of an ionic compound contains Avogadro’s number of formula units.1 mole NaCl = 6.02 x 1023 NaCl formula units1 mole K2SO4 = 6.02 x 1023 K2SO4 formula units

A Mole of a Compound

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Samples of 1 Mole Quantities

1 mole of C atoms = 6.02 x 1023 C atoms

1 mole of Al atoms = 6.02 x 1023 Al atoms

1 mole of S atoms = 6.02 x 1023 S atoms

1 mole of H2O molecules = 6.02 x 1023 H2O molecules

1 mole of CCl4 molecules = 6.02 x 1023 CCl4 molecules

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Avogadro’s number, 6.02 x 1023, can be written as anequality and two conversion factors.

Equality:1 mole = 6.02 x 1023 particles

Conversion Factors:6.02 x 1023 particles and 1 mole 1 mole 6.02 x 1023

particles

Avogadro’s Number

Using Avogadro’s Number

Avogadro’s number is used to o convert moles to particleso convert particles to moles

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Converting Moles to Particles

Avogadro’s number is used to convertmoles of a substance to particles.

How many Cu atoms are in 0.50 mole of Cu?

0.50 mole Cu x 6.02 x 1023 Cu atoms 1 mole Cu

= 3.0 x 1023 Cu atomsCopyright © 2009 by Pearson Education, Inc.

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Converting Particles to Moles

Avogadro’s number is used to convertparticles of a substance to moles.

How many moles of CO2 are in 2.50 x 1024 molecules CO2?

2.50 x 1024 molecules CO2 x 1 mole CO2

6.02 x 1023 molecules CO2

= 4.15 moles of CO2

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1. The number of atoms in 2.0 mole of Al atoms is A. 2.0 Al atoms.

B. 3.0 x 1023 Al atoms. C. 1.2 x 1024 Al atoms.

2. The number of moles of S in 1.8 x 1024 atoms of S is A. 1.0 mole of S atoms. B. 3.0 moles of S atoms. C. 1.1 x 1048 moles of S atoms.

Learning Check

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Subscripts and Moles

The subscripts in a formula show• the relationship of atoms in the formula.• the moles of each element in 1 mole of compound.

GlucoseC6H12O6

In 1 molecule: 6 atoms C 12 atoms H 6 atoms OIn 1 mole: 6 moles C 12 moles H 6 moles O

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Subscripts State Atoms and Moles

9 moles of C 8 moles of H 4 moles of O

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Factors from Subscripts

The subscripts are used to write conversion factors formoles of each element in 1 mole of a compound. Foraspirin, C9H8O4, the possible conversion factors are:

9 moles C 8 moles H 4 moles O 1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4

and

1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4 9 moles C 8 moles H 4 moles O

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Learning Check

A. How many moles of O are in 0.150 mole of aspirin, C9H8O4?

B. How many atoms of O are in 0.150 mole of aspirin, C9H8O4?

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5.2Molar Mass


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Molar Mass

The molar mass

• is the mass of 1 mole of an element or compound.

• is the atomic or molecular mass expressed in grams.


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Molar Mass from Periodic Table

Molar mass is the atomic mass expressed in grams.

1 mole of Ag 1 mole of C 1 mole of S = 107.9 g = 12.01 g = 32.07 g


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Give the molar mass for each (to the tenths decimal place).

A. 1 mole of K atoms = ________

B. 1 mole of Sn atoms = ________

Learning Check

Guide to Calculation Molar Mass of a Compound

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Molar Mass of a Compound

The molar mass of a compound is the sum of the molar masses of the elements in the formula.

Example: Calculate the molar mass of CaCl2.

Element Number of Moles

Atomic Mass Total Mass

Ca 1 40.1 g/mole 40.1 gCl 2 35.5 g/mole 71.0 gCaCl2 111.1 g

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Molar Mass of K3PO4

Calculate the molar mass of K3PO4.

Element Number of Moles

Atomic Mass Total Mass in K3PO4

K 3 39.1 g/mole 117.3 gP 1 31.0 g/mole 31.0 gO 4 16.0 g/mole 64.0 gK3PO4 212.3 g

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Some 1-mole Quantities

32.1 g 55.9 g 58.5 g 294.2 g 342.2 g

One-Mole Quantities


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What is the molar mass of each of the following?

A. K2O

B. Al(OH)3

Learning Check

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Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac?

1) 40.1 g/mole2) 262 g/mole 3) 309 g/mole

Learning Check

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Molar mass conversion factors • are fractions (ratios) written from the molar mass.• relate grams and moles of an element or compound.• for methane, CH4, used in gas stoves and gas heaters

is1 mole of CH4 = 16.0 g (molar mass

equality)

Conversion factors:16.0 g CH4 and 1 mole CH4

1 mole CH4 16.0 g CH4

Molar Mass Factors

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Acetic acid, C2H4O2, gives the sour taste to vinegar. Write two molar mass conversion factors for acetic acid.

Learning Check


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Molar mass factors are used to convert between the grams of a substance and the number of moles.

Calculations Using Molar Mass

Grams Molar mass factor Moles

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Aluminum is often used to build lightweight bicycleframes. How many grams of Al are in 3.00 mole of Al?

Molar mass equality: 1 mole of Al = 27.0 g of Al

Setup with molar mass as a factor:

3.00 mole Al x 27.0 g Al = 81.0 g of Al1 mole Al molar mass factor for Al

Moles to Grams

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Learning Check

Allyl sulfide, C6H10S, is a compound that has the odor of garlic. How many moles of C6H10S are in 225 g?


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Grams, Moles, and Particles

A molar mass factor and Avogadro’s number convert…

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Learning Check

How many H2O molecules are in 24.0 g of H2O?

1) 4.52 x 1023 H2O molecules



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Learning Check

If the odor of C6H10S can be detected from 2 x 10-13 g in 1 liter of air, how many molecules of C6H10S are present?

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5.3 Chemical Changes


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Physical Change

In a physical change,

• the state, shape, or size of the material changes.

• the identity and composition of the substance do not change.


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Chemical Change

In a chemical change,

• reacting substances form new substances with different compositions and properties.

• a chemical reaction takes place.


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Some Examples of Chemical and Physical Changes


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Classify each of the following as a 1) physical change or 2) chemical change.

A. ____Burning a candle.B. ____Ice melting on the street.

C. ____Toasting a marshmallow. D. ____Cutting a pizza. E. ____Polishing a silver bowl.

Learning Check

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Chemical Reaction

In a chemical reaction • a chemical change

produces one or more new substances.

• there is a change in the composition of one or more substances.


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Chemical Reaction

In a chemical reaction• old bonds are broken and new

bonds are formed.

• atoms in the reactants are rearranged to form one or more different substances.

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Chemical Reaction

In a chemical reaction

• the reactants are Fe and O2.

• the new product Fe2O3 is called rust.


1 chapter 5 chemical quantities and reactions 5.1 the mole copyright 2009 by pearson education, inc

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