Ch. 12 (Stoichiometry)

Chemists normally use an excess of one reactant in a chemical reaction because —

• the reaction will continue until all of the limiting reactant is consumed

• the reaction will continue until all of the excess reactant is consumed

• reactions do not take place unless there are unequal amounts of reactants

• reactions occur too quickly if equal amounts of reactants are used

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NGSS.HS-PS1-7

What is the first thing you must do to solve a stoichiometric problem?

• Find the limiting reactant.

• Find the excess reactant.

• Write a balanced chemical equation.

• Find the empirical formula.

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NGSS.HS-PS1-7

The actual yield of a product is

• a negative Value.

• a negative Value.

• the same as its theoretical yield.

• measured experimentally.

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NGSS.HS-PS1-6

1. Which of the following is a correct mole ratio for the following equation?

2Al(s) + 3Br₂(l) → 2AlBr₃(s)

• 2 mol Al : 3 mol Br

• 3 mol Br₂ : 2 mol Al

• 2 mol AlBr₃ : 1 mol Br₂

• 2 mol Br : 2 mol Al

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NGSS.HS-PS1-7

A chemical reaction equation must be ____ in order to make stoichiometric calculations.

• 1. measured

• 1. controlled

• 1. balanced

• produced

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How many moles of carbon dioxide is produced when 6.3 mol of propane gas is burned in excess oxygen?

C₃H₈ + 5O₂ →  3CO₂ + 4H₂O

• 2.1 mol

• 18.9 mol

• 6.3 mol

• 10.5 mol

You calculate the theoretical yield of a chemical reaction starting with 33.0g of reactant is 17.0g of product. What is the percent yield if the actual yield is 13.4g of product?

• 30.4%

• 131%

• 78.8%

• 40.6%

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NGSS.HS-PS1-7

The amount of product formed during a reaction depends on the

• 1. limiting reactant

• 1. excess reactant

• 1. reaction rate

• 1. None of these answers

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NGSS.HS-PS1-6

1. In the following reaction, how many moles of NaCN are required to react with 7 mol of Au?

4Au(s) + 8NaCN(aq) + O₂(g) + 2H₂O(l) → 4NaAu(CN)₂(aq) + 4NaOH(aq)  

• 14 mol

• 3.5 mol

• 7 mol

• 8 mol

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NGSS.HS-PS1-7

Stoichiometry is the study of quantitative relationships between amounts of —

• 1. the reactants and products of a chemical reaction relative to time

• 1. the products of a chemical reaction only

• 1. the reactants and products of a chemical reaction

• the reactants of a chemical reaction only

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