Question 1

A factory assembles cars using 4 tires and 1 steering wheel per car. If the factory has 40 tires and 15 steering wheels, what is the maximum number of complete cars that can be assembled, and which part is the limiting reactant?

Accepted Answer

10 cars; tires are the limiting reactant

Question 2

Which of the following best defines the limiting reactant in a chemical reaction?

Accepted Answer

The reactant that determines the amount of product formed

Question 3

Given the reaction $$\mathrm{CH_4$(g) + 2\ O_2$(g) \rightarrow CO_2$(g) + 2\ H_2O(g)}$$, if you start with 5 molecules of $$\mathrm{CH_4$}$$ and 8 molecules of $$\mathrm{O_2$}$$, what is the limiting reactant and how many molecules of $$\mathrm{CO_2$}$$ can be formed?

Accepted Answer

$$\mathrm{O_2$} is $$limiting; 4 molecules of $$\mathrm{CO_2$}$$

Question 4

For the reaction $$\mathrm{N_2$(g) + 3\ H_2$(g) \rightarrow 2\ NH_3$(g)}$$, if you have 3.00 mol of $$\mathrm{N_2$}$$ and 3.00 mol of $$\mathrm{H_2$}$$, what is the maximum amount of $$\mathrm{NH_3$}$$ that can be formed?

Accepted Answer

2.00 mol

Question 5

In the reaction $$3\ \mathrm{Si} + 2\ \mathrm{N_2$} \rightarrow \mathrm{Si_3N_4}$$, how many moles of $$\mathrm{Si_3N_4}$$ can be produced from 1.20 mol of Si and 1.00 mol of $$\mathrm{N_2$}$$?

Accepted Answer

0.400 mol

Question 6

A student expects to produce 64.0 g of methanol ($$\mathrm{CH_3OH}) $$from a reaction but only obtains 56.0 g. What is the percent yield?

Accepted Answer

$$87.5\%$$

Question 7

Benzene ($$\mathrm{C_6H_6}) $$reacts with excess bromine to form bromobenzene ($$\mathrm{C_6H_5Br}). If 8.00 g of $$benzene produces 12.85 g of bromobenzene, what is the percent yield? (Molar masses: $$\mathrm{C_6H_6} = 78.114\ g/mol$$, $$\mathrm{C_6H_5Br} = 157.010\ g/mol)$$

Accepted Answer

$$79.9\%$$

Question 8

In the reaction $$2\ \mathrm{Na(s)} + \mathrm{Cl_2$(g)} \rightarrow 2\ \mathrm{NaCl(s)}$$, if you start with 53.2 g Na and 65.8 g $$\mathrm{Cl_2$}$$, what is the theoretical yield of NaCl?

Accepted Answer

108 g

Question 9

For the reaction $$\mathrm{Cu_2O(s) + C(s) \rightarrow 2\ Cu(s) + CO(g)}$$, if you have 114.5 g $$\mathrm{Cu_2O}$$ and 11.5 g C, what is the limiting reactant?

Accepted Answer

$$\mathrm{Cu_2O}$$

Question 10

A reaction yields 87.4 g of Cu when the theoretical yield is 101.7 g. What is the percent yield?

Accepted Answer

$$85.9\%$$

Question 11

Silicon carbide ($$\mathrm{SiC}) is $$produced by reacting sand ($$\mathrm{$$SiO_2$$}) $$with carbon. If 100.0 kg of sand yields 51.4 kg of $$\mathrm{SiC}$$, and the theoretical yield is 66.7 kg, what is the percent yield?

Accepted Answer

$$77.0\%$$

Question 12

Given the reaction $$\mathrm{Na_2SiO_3(s) + 8\ HF(aq) \rightarrow H_2SiF_6(aq) + 2\ NaF(aq) + 3\ H_2O(l)}$$, how many moles of HF are needed to react with 0.300 mol $$\mathrm{Na_2SiO_3}$$?

Accepted Answer

2.40 mol

Question 13

How many grams of NaF are produced when 0.500 mol of HF reacts with excess $$\mathrm{Na_2SiO_3}$$? (Molar mass of NaF = 41.988 g/mol)

Accepted Answer

5.25 g

Question 14

How many grams of $$\mathrm{Na_2SiO_3}$$ can react with 0.800 g of HF? (Molar masses: HF = 20.0 g/mol, $$\mathrm{Na_2SiO_3} = 122.062 g/$$mol)

Accepted Answer

0.610 g

Question 15

Which of the following statements about actual yield and theoretical yield is correct?

Accepted Answer

Actual yield is always less than or equal to theoretical yield

Question 16

Why is the actual yield of a chemical reaction typically less than the theoretical yield?

Accepted Answer

Due to both controllable and uncontrollable factors such as incomplete reactions and side reactions

Question 17

If a reaction has a percent yield of 80% and the theoretical yield is 50 g, what is the actual yield?

Accepted Answer

40 g

Question 18

In a reaction, if the actual yield is 30 g and the percent yield is 60%, what is the theoretical yield?

Accepted Answer

50 g

Limiting Reactant, Theoretical Yield, and Percent Yield: Stoichiometry in Chemical Reactions

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