Stoichiometry: The math relationships betweensubstances involved in chemical reactions.

Stoichiometry allows us to make predictionsHow much of A do we need to make BHow much B can we produce if we start from BIf we have 40% yield, how much A must we

use in order to get 100 g B.If we have 20 grams of reactant A and 20 g of

reactant B, how much product will we make?

All stoichiometry problems are solved in a similar manneronce you learn the procedure, these problems will seem easy….. So…… Here we go!

1. How many grams of NaAlO2 can be obtained from 4.46 g of

aluminum chloride according to the following reaction?AlCl3 + 4 NaOH NaAlO2 + 3 NaCl + 2 H2O

? g4.46 g

gfw AlCl3

mole AlCl3

moleratio

mole NaAlO2

gfw NaAlO2

4.46 g AlCl3

Al = 27.03Cl = 3(35.4)133.2 g/mole

Mole AlCl3

133.2 g AlCl3

1mole NaAlO2

1 mole AlCl3

82.0g NaAlO2

Mole NaAlO2

Na = 23.0Al = 27.02O = 32.082g/mole NaAlO2

= 2.74 g NaAlO2

2. How many grams of hydrochloric acid are required to react completely with 61.8 g of calcium hydroxide?

2 HCl + Ca(OH)2 2 H2O + CaCl2

? g 61.8 g

gfw Ca(OH)2

mole Ca(OH)2

moleratio

mole HCl

gfw HCl

61.8 g Ca(OH)2

H = 1.0Cl = 35.4 36.4 g/mole HCl

Mole Ca(OH)2

74.0 g Ca(OH)2

2mole HCl

1 mole Ca(OH)2

36.4 g HCl

mole HCl

Ca = 40.12O = 32.02H = 2.074.0g/mole Ca(OH)2

= 60.8 g HCl

1. 3.How many grams of hydrogen are produced when 4.72 g of aluminum reacts with excess sulfuric acid?

2 Al + 3 H2SO4 3 H2 + Al2(SO4)3

? g4.72 g

gfw Al

mole Al

moleratio

mole H2

gfw H2

4.72 g Al

Al = 27.0 g/mole

mole Al

27.0 mole Al

3 mole H2

2mole Al

2.00 g H2

mole H2

2 H = 2.00 g/mole

= 0.524 g H2

4. The action of carbon monoxide on iron(III) oxide can be represented by the equation

Fe2O3 + CO Fe + CO2.

What is the minimum mass of carbon monoxide produced if 57.5 grams of iron were produced. (Hint) Make sure the equation is balanced before beginning.

Fe2O3 + 3 CO 2 Fe + 3 CO2

? g 57.5 g

gfw Fe

moles Fe

moleratio

moles CO

gfw CO

57.5 g Fe mole Fe

55.8 g Fe

3 mole CO

2 mole Fe

28.0 g CO

mole CO

C = 12.0O = 16.028 g/mole CO

6.Claude-Louis Berthollet first prepared ethyne (acetylene) by sparking carbon electrodes in hydrogen gas.

2C + H2 C2H2

How many grams of the carbon electrode will be consumed when 59.8 g of acetylene are produced?

Answer: 55.2 g C Show how we got this answer!