## Ch. 10 Stoichiometry

### 10.1 Interpreting a Chemical Equation

2 NO (g) + O 2 (g) → 2 NO 2 (g)

2 molecules 1 molecule 2 molecules 10 molecules 5 molecules 10 molecules 2 moles 1 mole 2 mole2

N 2 (g) + 3 H 2 (g) → 2 NH 3 (g)

___ molecule(s) ___ molecule(s) ___molecule(s) ____ mole ____ mole ____ mole

So coefficients give us molecule or mole ratios.

### 10.2 Mole-Mole Ratios

___ Fe 2 O 3 (s) + ___ CO (g)

g

1 mol 3 mol __ Fe (s) + ___CO 2 (g) 2 mol 3 mol

Examples:

1 mol Fe 2 O 3 mol CO 3 3 mol CO 1 mol Fe 2 O 3 2 mol Fe 3 mol CO

1. How many moles of iron can be formed from 10.2 moles of carbon monoxide?

10.2 mol CO ( 2 mol Fe / 3 mole CO) = 6.80 mol Fe 2. How many moles of iron(III) oxide are needed to form 17 moles of carbon dioxide?

17 mol CO 2 ( 1 mol Fe 2 O 3 / 3 mole CO 2 ) = 5.7 mol Fe 2 O 3

### Another Example

Balance this reaction: ___ SO 2 (g) + ___O 2 (g) g ___SO 3 (g) How many moles of SO 3 will form if 0.165 moles of oxygen gas react?

0.165 mol O 2 (2 mol SO 3 / 1 mol O 2 ) = 0.330 mol SO 3

How many moles of SO 2 are needed to make 0.042 moles of sulfur trioxide?

0.042 mol SO 3 (2 mol SO 2 / 2 mol SO 3 ) = 0.042 mol SO2

### 10.3-4 Mass – Mass Stoichiometry

Grams given Molar Mass Moles given Mole Ratio Moles find Molar Mass Grams find 3 FeO(s) + 2 Al(s)

g

3 Fe(s) + Al 2 O 3 (s) 1. Calculate the mass of iron (II) oxide needed to react completely with 5.55 g of aluminum.

2. Calculate the mass of aluminum oxide produced when 10.25 g of aluminum reacts completely.

3 FeO(s) + 2 Al(s)

g

3 Fe(s) + Al 2 O 3 (s) 1. 5.55 g Al

  mol Al 26.98

g Al      3 mol FeO 2 mol Al    =

22.2 g FeO

71.85

g FeO mol FeO

2. 10.25 g Al

  mol Al 26.98

g Al   =

19.37 g Al 2 O 3

1 mol Al 2 O 3 2 mol Al 101.96

g Al 2 O 3 mol Al 2 O 3

### 10.5-6 Mass – Volume and Volume-Volume problems

Write and balance the reaction of HCl (aq) and solid cobalt. Note cobalt will be +2 as an ion in this example.

2 HCl(aq) + Co(s)

g

CoCl 2 (aq) + H 2 (g) How many liters of gas at STP will form if 5.00 grams of cobalt reacts?

5.00 g Co(mol/58.93)(1 molH 2 /1molCo)(22.4L/mol) = 1.90 L H 2 If 2.374 L of hydrogen gas formed, how many grams of HCl reacted?

2.374 L H 2 (mol/22.4L)(2 mol HCl/1 mol H 2 )(36.46 g/mol) = 7.73 g HCl

### HCl gas plus oxygen gas produces chlorine gas and water vapor.

• How many liters of chlorine can be formed if 3.00 liters of oxygen react completely at STP?

4 HCl(g) + O 2 (g) g 2 Cl 2 (g) + 2 H 2 O(g) 3.00 L O 2 (mol / 22.4 L)(2 mol Cl 2 = 6.00 L Cl 2 / 1 mol O 2 )(22.4 L/mol)

## Try at Home

Carbon reacts with oxygen gas to form carbon monoxide. How many liters of carbon monoxide at STP can be made from 1. 15.0 grams carbon? 2. 20.0 liters of oxygen gas?

Remind me to show answers next time 2 C(s) + O 2 (g)

g

2 CO(g) 15.0 g C (mol /12.01g)(2 mol CO/2 mol C)(22.4 L / mol)= 28.0 L CO 20.0 L O 2 (mol /22.4L)(2 mol CO /1 mol O 2 )(22.4 L/mol)= 40.0 L CO

# Self Test

• Page 288 • Try 1-6, 10, 14 • Answers in Appendix J