Q: In a reaction, if the theoretical yield of a product is 10.0 g and the actual yield is 7.5 g, what is the percent yield?

$$\frac{7.5}{10.0} \times 100 = 75\%$$

Question 1

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

Accepted Answer

The reactant that is completely consumed and determines the maximum amount of product formed.

Question 2

In the reaction $$2 \mathrm{C}_4\mathrm{H}_{10} + 13 \mathrm{O}_2 \rightarrow 8 \mathrm{CO}_2 + 10 \mathrm{H}_2\mathrm{O}$$, if you start with 12.0 g of $$\mathrm{C}_4\mathrm{H}_{10}$$, 10.0 g of $$\mathrm{O}_2$$, and 5.0 g of $$\mathrm{H}_2\mathrm{O}$$, which reactant is the limiting reagent?

Accepted Answer

$$\mathrm{O}_2$$

Question 3

What is the first step in solving a limiting reagent problem?

Accepted Answer

Convert the given quantities to moles.

Question 4

Given the reaction $$2 \mathrm{Al} + 3 \mathrm{FeCl}_3 \rightarrow 2 \mathrm{AlCl}_3 + 3 \mathrm{Fe}$$, if 150 g of $$\mathrm{Al}$$ reacts with 420 g of $$\mathrm{FeCl}_3$$, what is the mass of the excess reactant remaining?

Accepted Answer

8.8 g

Question 5

In a reaction, if the theoretical yield of a product is 10.0 g and the actual yield is 7.5 g, what is the percent yield?

Accepted Answer

$$\frac{7.5}{10.0} 	imes 100 = 75\%$$

Question 6

Why is it important to identify the limiting reagent in industrial chemical processes?

Accepted Answer

To determine the maximum amount of product that can be formed.

Question 7

In the reaction $$\mathrm{Cr}_2\mathrm{O}_3 + 3 \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{Cr}_2\left(\mathrm{SO}_4\right)_3 + 3 \mathrm{H}_2\mathrm{O}$$, how many moles of $$\mathrm{H}_2\mathrm{SO}_4$$ are required to react completely with 2.0 moles of $$\mathrm{Cr}_2\mathrm{O}_3$$?

Accepted Answer

6.0 moles

Question 8

Acrylonitrile ($$\mathrm{C}_3\mathrm{H}_3\mathrm{N}) is $$produced by the reaction $$2 \mathrm{C}_4\mathrm{H}_{10} + 2 \mathrm{NH}_3 + 3 \mathrm{O}_2 \rightarrow 2 \mathrm{C}_3\mathrm{H}_3\mathrm{N} + 6 \mathrm{H}_2\mathrm{O}. If 12.0 g of$$ $$\mathrm{C}_4\mathrm{H}_{10}$$, 10.0 g of $$\mathrm{NH}_3$$, and 5.0 g of $$\mathrm{O}_2$$ react, what is the mass of acrylonitrile produced, assuming 100% yield?

Accepted Answer

15.1 g

Question 9

Which of the following is NOT a step in determining the limiting reagent?

Accepted Answer

Calculate the mass of the excess reagent.

Question 10

If a reaction has a limiting reagent, what happens to the other reactants?

Accepted Answer

They remain as excess after the reaction is complete.

Question 11

In a chemical reaction, why is it necessary to use balanced equations when performing mole-to-mole comparisons?

Accepted Answer

To ensure the law of conservation of mass is followed.

Question 12

A student mixes 5.0 g of $$\mathrm{Al}$$ with 10.0 g of $$\mathrm{FeCl}_3 in $$the reaction $$2 \mathrm{Al} + 3 \mathrm{FeCl}_3 \rightarrow 2 \mathrm{AlCl}_3 + 3 \mathrm{Fe}. $$Which reactant is in excess?

Accepted Answer

$$\mathrm{FeCl}_3$$

Question 13

If 2.0 moles of $$\mathrm{Cr}_2\mathrm{O}_3$$ react with 4.0 moles of $$\mathrm{H}_2\mathrm{SO}_4$$, which is the limiting reagent in the reaction $$\mathrm{Cr}_2\mathrm{O}_3 + 3 \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{Cr}_2\left(\mathrm{SO}_4\right)_3 + 3 \mathrm{H}_2\mathrm{O}$$?

Accepted Answer

$$\mathrm{H}_2\mathrm{SO}_4$$

Question 14

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 occur.

Question 15

In the context of limiting reagents, what does the term 'theoretical yield' refer to?

Accepted Answer

The maximum amount of product that can be formed from the limiting reagent.

Limiting Reactant and Mole-to-Mole Comparisons in Chemical Reactions

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