Question 1

Which statement best describes the limiting reagent in a chemical reaction?

Accepted Answer

It is the reactant that is completely consumed during the reaction.

Question 2

Given the reaction $\mathrm{Fe} + \mathrm{S} \rightarrow \mathrm{FeS}$, if you start with 3 moles of Fe and 1 mole of S, which is the limiting reagent?

Accepted Answer

S

Question 3

In a reaction, 9.87 moles of aluminum are added to hydrochloric acid. If the stoichiometric ratio requires more HCl than is available, which is the limiting reagent?

Accepted Answer

Hydrochloric acid

Question 4

For the reaction $\mathrm{Fe} + \mathrm{S} \rightarrow \mathrm{FeS}$, what is the theoretical yield of FeS if you start with 100 g of Fe and 100 g of S? (Molar masses: Fe = 55.85 g/mol, S = 32.07 g/mol)

Accepted Answer

$157\ \mathrm{g}$

Question 5

Which method can be used to identify the limiting reagent in a chemical reaction?

Accepted Answer

Compare the mole ratio of reactants to the stoichiometric ratio in the balanced equation.

Question 6

If 200 g of Fe and 100 g of S are reacted to form FeS, which reactant is in excess and how much FeS will be produced?

Accepted Answer

Fe is in excess; 157 g of FeS will be produced.

Question 7

A student mixes 5 moles of H$_2$ and 2 moles of O$_2$ to produce water. What is the limiting reagent? (Reaction: $2\mathrm{H}_2 + \mathrm{O}_2 \rightarrow 2\mathrm{H}_2\mathrm{O}$)

Accepted Answer

O$_2$

Question 8

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

Accepted Answer

To maximize the yield and minimize waste of reactants.

Question 9

In the reaction $\mathrm{Fe} + \mathrm{S} \rightarrow \mathrm{FeS}$, if you have 2 moles of Fe and 2 moles of S, how many moles of FeS can be produced?

Accepted Answer

2 moles

Question 10

A chemist wants to produce FeS using 50 g of Fe and 100 g of S. What is the limiting reagent and what mass of FeS will be produced? (Molar masses: Fe = 55.85 g/mol, S = 32.07 g/mol, FeS = 87.92 g/mol)

Accepted Answer

Fe is limiting; 78.7 g of FeS will be produced.

Question 11

Which of the following best explains why the limiting reagent determines the amount of product formed in a reaction?

Accepted Answer

Because it is the reactant that is completely consumed, stopping the reaction.

Question 12

In a laboratory, a student reacts 0.5 moles of Fe with 0.8 moles of S. What is the limiting reagent and how many moles of FeS will be formed?

Accepted Answer

Fe is limiting; 0.5 moles of FeS will be formed.

Question 13

A reaction requires a 1:1 mole ratio of reactants. If you have 2 moles of A and 3 moles of B, which is the limiting reagent?

Accepted Answer

A

Question 14

If a reaction produces less product than expected, which of the following is the most likely cause?

Accepted Answer

The limiting reagent was present in a smaller amount than required.

Question 15

In the reaction $2\mathrm{Al} + 6\mathrm{HCl} \rightarrow 2\mathrm{AlCl}_3 + 3\mathrm{H}_2$, if you have 9.87 moles of Al and 15 moles of HCl, which is the limiting reagent?

Accepted Answer

HCl

Question 16

A real-world application: In the production of iron sulfide (FeS) for industrial use, why is it important to calculate the limiting reagent before starting the reaction?

Accepted Answer

To ensure all reactants are completely used up and maximize product yield.

Question 17

If 100 g of Fe and 100 g of S are reacted, and the actual yield of FeS is 140 g, what is the percent yield? (Theoretical yield = 157 g)

Accepted Answer

$89.2\%$

Question 18

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

Accepted Answer

Calculate the density of each reactant.

Question 19

A reaction between 0.2 moles of Fe and 0.3 moles of S produces FeS. How many moles of FeS are formed and which reactant is in excess?

Accepted Answer

0.2 moles of FeS; S is in excess.

Limiting Reagents and Limiting Reactant Calculations

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