Stoichiometry

If a chemist calculates the maximum amount of product that could be obtained in a chemical reaction, he or she is calculating the

• theoretical yield
• mole ratio
• actual yield
• percentage yield

2 KClO₃ → 2 KCl + 3 O₂
How many moles of oxygen are produced when 6.7 moles of KClO₃ decompose completely?

• 6.7 mol
• 1.0 mol
• 10.1 mol
• 4.5 mol

2Na + 2H₂O → 2NaOH+ H₂
How many grams of hydrogen are produced if 120 g of Na are available?

• 5.2 g
• 2.6 g
• 690 g
• 45 g

Cl₂ + 2 KBr → Br₂ + 2 KCl
How many grams of potassium chloride can be produced from 356 g of chlorine and 356 g of potassium bromide?

• 749 g
• 223 g
• 479 g
• 814 g

A chemist interested in the efficiency of a chemical reaction would calculate the

• mole ratio
• rate of reaction
• percent yield
• energy released

Fe (s) + S (l) --> FeS (s)  

In the experiment above, 7.62 g of Fe are allowed to react with 8.67 g of S.
How much FeS is formed?

• 14.8 g
• 12.0 g

• 13.7 g
• 19.9 g

When does a chemical reaction stop?

• When the lab is finished
• When the excess reactant is used up
• When the limiting reactant is used up
• Chemical reactions never stop

2Al + 6HCl --> 2AlCl₃ + 3H₂

Aluminium reacts with hydrochloric acid. How many grams of aluminum are necessary to produce 11 L of hydrogen gas at STP?

• 13

• 8.8

• 0.99

• 1.0

1Mg + 2H₂O --> Mg(OH)₂ + H₂

What volume of hydrogen will be produced at STP by the reaction 67.3 g of magnesium?

• 62.0 L

• 0.12 L

• 2.77 L

• 1.15 L

When reacting Na with Cl₂, we calculated that the theoretical yield should be 13 grams. Our actual yield was 12.5 grams. What is the percent yield?

• 90.4%

• 104%

• 96.15%

• 1.04%