LecturePLUS Timberlake 99 1

Chapter 5Chemical Reactions and

Quantities

Mole Relationships in Chemical Equations

LecturePLUS Timberlake 99 2

Mole-Mole Factors

Show the mole-to-mole ratio between two

of the substances in a balanced equation

Use the coefficients of two substances in

the equation

LecturePLUS Timberlake 99 3

Writing Mole Factors

4 Fe + 3 O2 2 Fe2O3

Fe and O2 4 mole Fe and 3 mole O2

3 mole O2 4 mole Fe

Fe and Fe2O3 4 mole Fe and 2 mole Fe2O3

2 mole Fe2O3 4 mole Fe

O2 and Fe2O3 3 mole O2 and 2 mole Fe2O3

2 mole Fe2O3 3 mole O2

LecturePLUS Timberlake 99 4

Learning Check S1

3 H2(g) + N2(g) 2 NH3(g)

A. A mole factor for H2 and N2 is

1) 3 mole N2 2) 1 mole N2 3) 1 mole N2

1 mole H2 3 mole H2 2 mole H2

B. A mole factor for NH3 and H2 is

1) 1 mole H2 2) 2 mole NH3 3) 3 mole N2

2 mole NH3 3 mole H2 2 mole NH3

LecturePLUS Timberlake 99 5

Solution S1

3 H2(g) + N2(g) 2 NH3(g)

A. A mole factor for H2 and N2 is

2) 1 mole N2

3 mole H2

B. A mole factor for NH3 and H2 is

2) 2 mole NH3

3 mole H2

LecturePLUS Timberlake 99 6

Chemical Calculations

4 Fe + 3 O2 2 Fe2O3

How many moles of Fe2O3 are produced when

6.0 moles O2 react?

6.0 mole O2 x 2 mole Fe2O3 = 4.0 mole Fe2O3

3 mole O2

LecturePLUS Timberlake 99 7

Learning Check S2

4 Fe + 3 O2 2 Fe2O3

How many moles of Fe are needed to react with 12.0

mole of O2?

1) 3.00 mole Fe

2) 9.00 mole Fe

3) 16.0 mole Fe

LecturePLUS Timberlake 99 8

Solution S2

4 Fe + 3 O2 2 Fe2O3

12.0 mole O2 x 4 mole Fe = 16.0 mole Fe

3 mole O2

LecturePLUS Timberlake 99 9

Learning Check S 3

4 Fe + 3 O2 2 Fe2O3

How many grams of O2 are needed to produce 0.400 mole of

Fe2O3?

1) 38.4 g O2

2) 19.2 g O2

3) 1.90 g O2

LecturePLUS Timberlake 99 10

Solution S 3

2) 19.2 g O2

0.400 mole Fe2O3 x 3 mole O2 x 32.0 g O2

2 mole Fe2O3 1 mole O2

= 19.2 g O2

LecturePLUS Timberlake 99 11

Mass of A Reaction

The reaction between H2 and O2 produces

13.1 g of water. How many grams of O2

reacted?

Write the equation

H2 (g) + O2 (g) H2O (g)

Balance the equation

2 H2 (g) + O2 (g) 2 H2O (g)

LecturePLUS Timberlake 99 12

Organize data mole bridge

2 H2 (g) + O2 (g) 2 H2O (g)

? g 13.1 g

Plan g H2O mole H2O mole O2 O2

Setup

13.1 g H2O x 1 mole H2O x 1 mole O2 x 32.0 g O2

18.0 g H2O 2 mole H2O 1 mole O2

= 11.6 g O2

LecturePLUS Timberlake 99 13

Points to Remember

1. Read an equation in moles2. Convert given amount to moles3. Use mole factor to give desired moles4. Convert moles to grams

grams (given) grams (desired)

moles (given) moles (desired)

LecturePLUS Timberlake 99 14

Learning Check S 4

How many grams of O2 are need to react

50.0 grams of Na in the reaction

4 Na + O2 2 Na2O

Complete the set up:

50.0 g Na x 1 mole Na x ________ x _______

23.0 g Na

LecturePLUS Timberlake 99 15

Solution S 4

4 Na + O2 2 Na2O

50.0 g Na x 1 mole Na x 1 mole O2 x 32.0 g

23.0 g Na 4 mole Na 1 mole O2

= g O2

LecturePLUS Timberlake 99 16

Learning Check S5

Acetylene gas C2H2 burns in the oxyactylene

torch for welding. How many grams of C2H2 are

burned if the reaction produces 75.0 g of CO2?

2 C2H2 + 5 O2 4 CO2 + 2 H2O

LecturePLUS Timberlake 99 17

Solution S5

2 C2H2 + 5 O2 4 CO2 + 2 H2O

75.0 g CO2 x 1 mole CO2 x 2 mole C2H2 x 26.0 g C2H2

44.0 g CO2 4 mole CO2 1 mole C2H2

= 22.2 g C2H2

LecturePLUS Timberlake 99 18

Pathways for Problems Using Equations

Given (A) Find (B)

grams (A) grams (B)

moles (A) moles (B)

particles (A) particles (B)

LecturePLUS Timberlake 99 19

Pathways for Problems Using Equations

Given (A) Find (B)

grams (A) grams (B)

molar molar

mass (A) mass (B)

coefficients

moles (A) moles (B)

Avogadro's Avogradro’s

number number

particles (A) particles (B)