Q: Which equation is used to calculate percent yield in a chemical reaction?

$$\displaystyle \%\ \mathrm{yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100$$

Question 1

A chemical reaction is carried out by mixing 10.0 g of hydrogen gas ($$\mathrm{H_2$}) $$with 80.0 g of oxygen gas ($$\mathrm{O_2$}) to $$produce water ($$\mathrm{H_2O}). $$Which reactant is the limiting reactant?

Accepted Answer

Hydrogen gas ($$\mathrm{H_2$})$$

Question 2

If 4.00 g of methane ($$\mathrm{CH_4$}) $$reacts with excess oxygen at STP, what volume of carbon dioxide ($$\mathrm{CO_2$}) $$gas is produced? ($$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O})$$

Accepted Answer

$$5.60\ \mathrm{L}$$

Question 3

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

Accepted Answer

The reactant that is completely consumed first, limiting the amount of product formed

Question 4

A reaction has a theoretical yield of 50.0 g, but only 42.0 g of product is actually obtained. What is the percent yield?

Accepted Answer

$$84.0\%$$

Question 5

In the reaction $$\mathrm{N_2$ + 3H_2 \rightarrow 2NH_3}$$, if you start with 28.0 g of $$\mathrm{N_2$}$$ and 6.0 g of $$\mathrm{H_2$}$$, which reactant is in excess?

Accepted Answer

$$\mathrm{H_2$}$$

Question 6

Which equation is used to calculate percent yield in a chemical reaction?

Accepted Answer

$$\displaystyle \%\ \mathrm{yield} = \frac{	ext{actual yield}}{	ext{theoretical yield}} 	imes 100$$

Question 7

At STP, what volume of oxygen gas ($$\mathrm{O_2$}) is $$required to completely react with 44.0 g of propane ($$\mathrm{C_3H_8}) $$according to the equation $$\mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O}$$?

Accepted Answer

$$112\ \mathrm{L}$$

Question 8

Which of the following is a correct step in solving a mass-mass stoichiometry problem?

Accepted Answer

Convert the given mass to moles using molar mass

Question 9

A reaction between 10.0 g of $$\mathrm{$$CaCO_3$$}$$ and excess $$\mathrm{HCl}$$ produces $$\mathrm{CO_2$}$$ gas. What volume of $$\mathrm{CO_2$} is $$produced at STP? ($$\mathrm{$$CaCO_3$$ + 2HCl \rightarrow $$CaCl_2$$ + CO_2$ + H_2O})$$

Accepted Answer

$$2.24\ \mathrm{L}$$

Question 10

In a volume-volume stoichiometry problem at STP, what is the ratio of volumes of reactants and products equivalent to?

Accepted Answer

The ratio of their coefficients in the balanced equation

Question 11

A student mixes 50.0 g of $$\mathrm{NaCl}$$ with 100.0 g of $$\mathrm{$$AgNO_3$$} to $$produce $$\mathrm{AgCl}$$ and $$\mathrm{$$NaNO_3$$}. If $$the actual yield of $$\mathrm{AgCl} is 60.0 g$$, but the theoretical yield is 70.0 g, what is the percent yield?

Accepted Answer

$$85.7\%$$

Question 12

Which of the following statements about excess reactant is correct?

Accepted Answer

It is the reactant that remains after the reaction is complete

Question 13

If 10.0 L of $$\mathrm{H_2$}$$ gas reacts with 5.0 L of $$\mathrm{O_2$}$$ gas at STP to form water vapor, what is the limiting reactant?

Accepted Answer

$$\mathrm{O_2$}$$

Question 14

A reaction produces 15.0 g of product, but the theoretical yield is 20.0 g. What is the percent yield?

Accepted Answer

$$75.0\%$$

Question 15

Which of the following is NOT a step in solving a limiting reactant problem?

Accepted Answer

Assume all reactants are in excess

Question 16

In the reaction $$\mathrm{2H_2 + O_2$ \rightarrow 2H_2O}$$, what volume of $$\mathrm{H_2$}$$ gas at STP is needed to react completely with 11.2 L of $$\mathrm{O_2$}$$ gas?

Accepted Answer

$$22.4\ \mathrm{L}$$

Question 17

A student calculates the theoretical yield of a reaction to be 25.0 g, but only 20.0 g is obtained. Which of the following best explains the difference?

Accepted Answer

The reaction was not 100% efficient due to side reactions or incomplete conversion

Question 18

Which of the following is true about volume-volume stoichiometry at STP?

Accepted Answer

Volumes of gases can be directly related using the coefficients in the balanced equation

Question 19

A reaction between 8.0 g of $$\mathrm{H_2$}$$ and 32.0 g of $$\mathrm{O_2$}$$ produces water. What is the maximum mass of water that can be formed?

Accepted Answer

$$36.0\ \mathrm{g}$$

Stoichiometry: Quantitative Relationships in Chemical Reactions

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