Q: Which of the following is the correct formula for percent yield?

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

Question 1

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

Accepted Answer

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

Question 2

Given the reaction $$2 \mathrm{ZnS} (s) + 3 \mathrm{O}_2 (g) ightarrow 2 \mathrm{ZnO} (s) + 2 \mathrm{SO}_2 (g)$$, how many kilograms of $$\mathrm{O}_2$$ are required to react completely with $$5.00 	imes 10^3$ g of $$\mathrm{ZnS}$$?

Accepted Answer

$$2.46 kg$$

Question 3

A mixture of $$15.0 g of$$ $$\mathrm{CS}_2$$ and $$35.0 g of$$ $$\mathrm{O}_2$$ reacts according to $$\mathrm{CS}_2 (g) + 3 \mathrm{O}_2 (g) \rightarrow \mathrm{CO}_2 (g) + 2 \mathrm{SO}_2 (g). $$How many grams of $$\mathrm{SO}_2$$ are produced?

Accepted Answer

$$25.2 g$$

Question 4

In the reaction $$\mathrm{Zn} (s) + 2 \mathrm{HCl} (aq) \rightarrow \mathrm{ZnCl}_2 (aq) + \mathrm{H}_2 (g)$$, if $$0.30$$ mol of Zn is added to $$0.52$$ mol of HCl, how many moles of $$\mathrm{H}_2$$ are produced?

Accepted Answer

$$0.26$$ mol

Question 5

Which of the following is the correct formula for percent yield?

Accepted Answer

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

Question 6

A student reacts $$0.800 g of $$sodium hydrogen carbonate with excess hydrochloric acid and obtains $$0.420 g of $$sodium chloride. What is the percent yield of sodium chloride? (Theoretical yield is $$0.556 g.)$$

Accepted Answer

$$75.5\%$$

Question 7

Which of the following steps is NOT part of the standard procedure for solving a stoichiometry problem?

Accepted Answer

Estimate the product yield based on color change.

Question 8

In a reaction, $$10$$ moles of $$\mathrm{H}_2$$ and $$7$$ moles of $$\mathrm{O}_2$$ are mixed and react according to $$2 \mathrm{H}_2 + \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O}. $$After the reaction, how many moles of $$\mathrm{O}_2$$ remain?

Accepted Answer

$$2$$ moles

Question 9

Which real-world process is an example of a chemical reaction used to reduce environmental pollution by removing sulfur dioxide from power plant exhaust?

Accepted Answer

Flue gas desulfurization

Question 10

If $$1.50 g of $$salicylic acid ($$\mathrm{C}_7\mathrm{H}_6\mathrm{O}_3) $$reacts with $$11.20 g of $$methanol ($$\mathrm{CH}_3\mathrm{OH}) to $$produce $$1.31 g of $$methyl salicylate ($$\mathrm{C}_8\mathrm{H}_8\mathrm{O}_3$$), what is the percent yield?

Accepted Answer

$$79.2\%$$

Question 11

Which of the following best explains why the actual yield of a chemical reaction is often less than the theoretical yield?

Accepted Answer

Side reactions and incomplete reactions can reduce the amount of product formed.

Question 12

In the flue gas desulfurization process, what is the role of calcium carbonate ($$\mathrm{CaCO}_3$$)?

Accepted Answer

It reacts with sulfur dioxide to form calcium sulfate hydrate (gypsum).

Question 13

A pizza recipe requires 1 crust, 5 oz tomato sauce, and 2 cups cheese per pizza. If you have 10 cups cheese, dough for 6 crusts, and 50 oz sauce, what is the maximum number of pizzas you can make?

Accepted Answer

5

Question 14

Which of the following conversions is NOT part of the 'mole bridge' in stoichiometric calculations?

Accepted Answer

Grams to liters using density

Question 15

In the reaction $$2 \mathrm{SO}_2 (g) + 2 \mathrm{CaCO}_3 (s) + 2 \mathrm{H}_2\mathrm{O} (l) + \mathrm{O}_2 (g) \rightarrow 2 \mathrm{CaSO}_4 \cdot 2\mathrm{H}_2\mathrm{O} (s) + 2 \mathrm{CO}_2 (g)$$, how many moles of $$\mathrm{CaCO}_3$$ are needed to react with $$4$$ moles of $$\mathrm{SO}_2$$?

Accepted Answer

4 moles

Question 16

Which of the following statements about excess reactants is correct?

Accepted Answer

Excess reactants remain after the limiting reactant is used up.

Question 17

A chemical reaction has a theoretical yield of $$10.0 g $$and an actual yield of $$7.5 g. $$What is the percent yield?

Accepted Answer

$$75\%$$

Question 18

Which of the following is the correct balanced equation for the reaction of manganese dioxide with hydrochloric acid to produce chlorine gas?

Accepted Answer

$$4 \mathrm{HCl} + \mathrm{MnO}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} + \mathrm{MnCl}_2 + \mathrm{Cl}_2$$

Stoichiometry, Limiting Reactants, and Reaction Yield in General Chemistry

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