Question 1

Which of the following best describes the law of conservation of mass as it applies to balancing chemical equations?

Accepted Answer

The total mass of reactants must equal the total mass of products in a chemical reaction.

Question 2

Balance the following equation: $$\mathrm{C_3H_8 + O_2$ \rightarrow CO_2$ + H_2O}. $$What is the correct set of coefficients?

Accepted Answer

$$1, 5, 3, 4$$

Question 3

In the reaction $$\mathrm{2Al + 3Cl_2 \rightarrow 2AlCl_3}$$, how many moles of $$\mathrm{Cl_2$}$$ are required to react completely with 4 moles of $$\mathrm{Al}$$?

Accepted Answer

6 moles

Question 4

Which of the following is the correct balanced equation for the reaction between calcium hydroxide and phosphoric acid to form calcium phosphate and water?

Accepted Answer

$$3\mathrm{Ca(OH)_2} + 2\mathrm{H_3PO_4} \rightarrow \mathrm{Ca_3$(PO_4$)_2} + 6\mathrm{H_2O}$$

Question 5

A reaction produces 44.0 g of $$\mathrm{CO_2$}$$ from 12.0 g of $$\mathrm{C}$$ and excess $$\mathrm{O_2$}. $$What is the percent yield if the theoretical yield is 44.0 g?

Accepted Answer

100%

Question 6

Which of the following steps is NOT part of the systematic approach to balancing chemical equations?

Accepted Answer

Changing the subscripts of compounds to balance atoms

Question 7

Given the reaction $$\mathrm{2KClO_3 \rightarrow 2KCl + 3O_2}$$, how many grams of $$\mathrm{O_2$}$$ are produced from 12.25 g of $$\mathrm{$$KClO_3$$}$$? (Molar masses: $$\mathrm{$$KClO_3$$} = 122.5 g/$$mol, $$\mathrm{O_2$} = 32.0 g/$$mol)

Accepted Answer

1.60 g

Question 8

In a limiting reagent problem, which of the following statements is correct?

Accepted Answer

The limiting reagent is completely consumed in the reaction.

Question 9

If 10.0 g of $$\mathrm{C}$$ reacts with 80.0 g of $$\mathrm{O_2$} to $$form $$\mathrm{CO_2$}$$, which reactant is the limiting reagent? (Molar masses: $$\mathrm{C} = 12.0 g/$$mol, $$\mathrm{O_2$} = 32.0 g/$$mol)

Accepted Answer

$$\mathrm{C}$$

Question 10

Which of the following best describes a mole-to-mole conversion in stoichiometry?

Accepted Answer

Using the coefficients from a balanced equation to relate the moles of one substance to the moles of another.

Question 11

A reaction has the following balanced equation: $$\mathrm{2H_2 + O_2$ \rightarrow 2H_2O}. If $$you start with 4 moles of $$\mathrm{H_2$}$$ and 1 mole of $$\mathrm{O_2$}$$, what is the limiting reagent?

Accepted Answer

$$\mathrm{O_2$}$$

Question 12

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

Accepted Answer

Mass of A $$\rightarrow$$ Moles of A $$\rightarrow$$ Moles of B $$\rightarrow$$ Mass of B

Question 13

In the reaction $$\mathrm{N_2$ + 3H_2 \rightarrow 2NH_3}$$, how many grams of $$\mathrm{NH_3$}$$ can be produced from 14.0 g of $$\mathrm{N_2$}$$ and excess $$\mathrm{H_2$}$$? (Molar mass: $$\mathrm{N_2$} = 28.0 g/$$mol, $$\mathrm{NH_3$} = 17.0 g/$$mol)

Accepted Answer

17.0 g

Question 14

Which of the following is a correct example of a real-world limiting reagent scenario?

Accepted Answer

Making cars with a limited number of tires and chassis.

Question 15

Given the reaction $$\mathrm{2Al + 3S \rightarrow Al_2S_3}$$, how many grams of $$\mathrm{Al_2S_3}$$ are produced from 10.8 g of $$\mathrm{Al}$$ and 16.0 g of $$\mathrm{S}$$? (Molar masses: $$\mathrm{Al} = 27.0 g/$$mol, $$\mathrm{S} = 32.0 g/$$mol, $$\mathrm{Al_2S_3} = 150.0 g/$$mol)

Accepted Answer

30.0 g

Question 16

Which of the following is the correct balanced equation for the combustion of methane?

Accepted Answer

$$\mathrm{CH_4$ + 2O_2 \rightarrow CO_2$ + 2H_2O}$$

Question 17

A solution contains 0.50 mol of $$\mathrm{NaCl} in 250 mL of $$water. What is the molarity of the solution?

Accepted Answer

2.0 M

Question 18

Which of the following is the correct mole ratio for $$\mathrm{C_2H_6 + 7/2 O_2$ \rightarrow 2CO_2 + 3H_2O}$$?

Accepted Answer

1 : 3.5 : 2 : 3

Question 19

If 5.0 g of $$\mathrm{C_6H_{12}O_6$} is $$completely combusted, how many grams of $$\mathrm{CO_2$}$$ are produced? (Balanced equation: $$\mathrm{C_6H_{12}O_6$} + 6O_2 \rightarrow 6CO_2 + 6H_2O}$$; Molar masses: $$\mathrm{C_6H_{12}O_6$} = 180 g/$$mol, $$\mathrm{CO_2$} = 44 g/$$mol)

Accepted Answer

1.47 g

Balancing Chemical Equations and Reaction Stoichiometry: Study Notes

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