Question 1

Which of the following statements about a balanced chemical equation is TRUE?

Accepted Answer

It shows the ratio of moles of reactants and products.

Question 2

Given the reaction $$5KI + $$KIO_3$$ + 6HNO_3 \rightarrow 6KNO_3 + 3I_2 + 3H_2O$$, how many moles of $$I_2$$ are produced from 0.0789 mol KI?

Accepted Answer

$$0.04735$$ mol $$I_2$$

Question 3

In the reaction $$N_2 (g) + 3H_2 (g$$) \rightarrow 2NH_3 (g)$$, if you react 5 mol N_2$ with 9 mol H_2$, which is the limiting reagent and how many moles of excess reactant remain?

Accepted Answer

$$H_2 is $$limiting, 4 moles of $$N_2$$ remain

Question 4

A student mixes 13.10 g KI with excess $$KIO_3$$ and $$HNO_3. $$What mass of $$I_2 is $$produced? (Molar masses: $$KI = 166.0 g/$$mol, $$I_2 = 253.8$ g/mol)

Accepted Answer

$$12.02 g$$ $$I_2$$

Question 5

If you start with 4.28 g of $$KIO_3$$ and all the KI has reacted, how much $$KIO_3$$ remains? (Molar mass $$KIO_3 = 214.0$ g/mol, 0.01578$ mol $$KIO_3$$ reacted)

Accepted Answer

$$0.90 g$$ $$KIO_3$$

Question 6

Which of the following is the correct sequence for solving a mass-to-mass stoichiometry problem?

Accepted Answer

Convert grams of A to moles of A, use stoichiometric ratio to find moles of B, convert moles of B to grams of B.

Question 7

In the reaction $$2Ca_3(PO_4$)_2 + 6SiO_2 + 10C \rightarrow 6CaSiO_3 + 10CO + P_4$, if you have 6.00 g Ca_3$(PO_4$)_2$$, 4.00 g $$SiO_2$$, and 1.00 g C, which is the limiting reagent?

Accepted Answer

$$Ca_3$$($$PO_4)_2$

Question 8

What is the maximum mass of $$P_4$$ that can be produced from the reaction above, given the limiting reagent is $$Ca_3$$($$PO_4)_2$ and 0.00970$ mol P_4$ is formed? (Molar mass P_4$ = 123.9 g/$$mol)

Accepted Answer

$$1.20 g$

Question 9

In a two-step reaction to prepare $$PCl_3$$, starting with 10.0 g HCl and 6.08 g $$MnO_2$$, which is the limiting reagent?

Accepted Answer

$$HCl$$

Question 10

Given the limiting reagent is HCl and $$0.0457$$ mol $$PCl_3 is $$produced, what is the maximum mass of $$PCl_3$$ that can be prepared? (Molar mass $$PCl_3 = 137.4$ g/mol)

Accepted Answer

$$6.28 g$

Question 11

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

Accepted Answer

It is the reactant that is completely consumed, determining the amount of product formed.

Question 12

A reaction has excess $$KIO_3$$ and $$HNO_3$$, but limited KI. What governs the amount of $$I_2$$ produced?

Accepted Answer

The amount of KI used

Question 13

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

Accepted Answer

Select the reactant with the largest mole-coefficient ratio as the limiting reagent

Question 14

In the combustion of methane $$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$, how many moles of water are produced from 2 moles of methane?

Accepted Answer

4 moles

Question 15

A chemical grill uses $$C_3H_8$$ and $$O_2 to $$produce $$CO_2$$ and $$H_2O. If 1 $$mol $$C_3H_8$$ reacts with 2 mol $$O_2$$, what is the limiting reagent?

Accepted Answer

$$O_2$$

Question 16

Why is it important to identify the limiting reagent in a chemical reaction?

Accepted Answer

To calculate the maximum amount of product that can be formed

Question 17

If a reaction starts with 0.0194 mol $$Ca_3$$($$PO_4)_2$, 0.0666 mol $$SiO_2$$, and 0.0833 mol C, which mole-coefficient ratio indicates the limiting reagent?

Accepted Answer

$$0.0097$$ for $$Ca_3$$($$PO_4)_2$

CH 4-3: Chemical Reactions and Stoichiometry: Mass Relationships and Limiting Reagents

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