Q: Given the reaction $$2 \mathrm{NaN}_3 (s) \rightarrow 2 \mathrm{Na} (s) + 3 \mathrm{N}_2 (g)$$, how many grams of sodium azide ($$\mathrm{NaN}_3$$, MM = 65.02 g/mol) are required to produce 30.0 g of nitrogen gas ($$\mathrm{N}_2$$, MM = 28.02 g/mol)?

$$30.0 \text{ g } \mathrm{N}_2 \times \frac{1 \text{ mol } \mathrm{N}_2}{28.02 \text{ g } \mathrm{N}_2} \times \frac{2 \text{ mol } \mathrm{NaN}_3}{3 \text{ mol } \mathrm{N}_2} \times 65.02 \text{ g } \mathrm{NaN}_3 = 46.4 \text{ g } \mathrm{NaN}_3$$

Q: Calculate the percent by mass of sulfur in Al$$_2(SO$_4$$)$$_3 (MM = 342.15 g/$$mol).

$$\frac{3 \times 32.07}{342.15} \times 100 = 28.15\%$$

Q: A sample contains 14.3 mL of 0.410 M Ca(NO$$_3$$)$$_2. $$How many molecules of Ca(NO$$_3$$)$$_2$$ are present?

$$0.0143 \text{ L} \times 0.410 \text{ mol/L} \times 6.022 \times 10$$^{23}$$ = 3.53 \times 10$$^{21}$$ molecules

Q: How many moles of oxygen are in 45.0 grams of CaCO$$_3 (MM = 100.1 g/$$mol)?

$$45.0 \text{ g} \times \frac{1 \text{ mol}}{100.1 \text{ g}} \times \frac{3 \text{ mol O}}{1 \text{ mol CaCO}_3} = 1.35 \text{ mol O}$$

Q: What is the theoretical yield of Fe (in mol) that can be produced from the reaction of 2.00 mol Fe$$_2O$_3$$ with 3.00 mol CO? $$Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$$

3.00 mol CO \times \frac{2 \text{ mol Fe}}{3 \text{ mol CO}} = 2.00 \text{ mol Fe}$

Q: How many moles of CO$$_2$$ are produced when 2.0875 moles of methanol ($$CH_3OH) $$are completely combusted? $$2CH_3OH + 3O_2 \rightarrow 2CO_2 + 4H_2O$$

$$2.0875 \text{ mol CH}_3\text{OH} \times \frac{2 \text{ mol CO}_2}{2 \text{ mol CH}_3\text{OH}} = 2.0875 \text{ mol CO}_2$$

Question 1

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

Accepted Answer

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

Question 2

Given the reaction $$2 \mathrm{NaN}_3 (s) \rightarrow 2 \mathrm{Na} (s) + 3 \mathrm{N}_2 (g)$$, how many grams of sodium azide ($$\mathrm{NaN}_3$$, MM = 65.02 g/mol) are required to produce 30.0 g of nitrogen gas ($$\mathrm{N}_2$$, MM = 28.02 g/mol)?

Accepted Answer

$$30.0 	ext{ g } \mathrm{N}_2 	imes \frac{1 	ext{ mol } \mathrm{N}_2}{28.02 	ext{ g } \mathrm{N}_2} 	imes \frac{2 	ext{ mol } \mathrm{NaN}_3}{3 	ext{ mol } \mathrm{N}_2} 	imes 65.02 	ext{ g } \mathrm{NaN}_3 = 46.4 	ext{ g } \mathrm{NaN}_3$$

Question 3

A solution is prepared by diluting 250.0 mL of 11.3 M HNO$$_3 to a $$final volume of 500.0 mL. What is the concentration (M) of the diluted solution?

Accepted Answer

$$M_1$$ $$V_1$$ = $$M_2$$ $$V_2$$ \Rightarrow $$M_2$$ = \frac{$$M_1$$ $$V_1$$}{$$V_2$$} = \frac{11.3 	imes 250.0}{500.0} = 5.65 	ext{ M}$$

Question 4

Which of the following compounds is insoluble in water?

Accepted Answer

PbSO$$_4$$

Question 5

What is the net ionic equation for the reaction between H$$_2SO$_4$$ and Ba(OH)$$_2$$?

Accepted Answer

$$2 \mathrm{H}^+ (aq) + 2 \mathrm{OH}^- (aq) \rightarrow 2 \mathrm{H}_2\mathrm{O} (l)$$

Question 6

Which of the following is a strong acid?

Accepted Answer

HNO$$_3$$

Question 7

Calculate the percent by mass of sulfur in Al$$_2(SO$_4$$)$$_3 (MM = 342.15 g/$$mol).

Accepted Answer

$$\frac{3 	imes 32.07}{342.15} 	imes 100 = 28.15\%$$

Question 8

A sample contains 14.3 mL of 0.410 M Ca(NO$$_3$$)$$_2. $$How many molecules of Ca(NO$$_3$$)$$_2$$ are present?

Accepted Answer

$$0.0143 	ext{ L} 	imes 0.410 	ext{ mol/L} 	imes 6.022 	imes 10$$^{23}$$ = 3.53 	imes 10$$^{21}$$ molecules

Question 9

Which element is being oxidized in the reaction $$Cr_2O_3 + 4 $$HNO_3$$ \rightarrow 2 Cr(NO_3$)_2 + 2 NO_2$ + 2 H_2O$$?

Accepted Answer

Nitrogen (N)

Question 10

What is the oxidation number of Mn in KMnO$$_4$$?

Accepted Answer

+7

Question 11

Which of the following solutions will result in the formation of a precipitate when added to K$$_2SO$_4(aq$$)?

Accepted Answer

BaCl$$_2(aq)$$

Question 12

A compound contains 40.0% C, 6.7% H, and 53.3% O by mass. What is its empirical formula?

Accepted Answer

CH$$_2O$$

Question 13

Which of the following is a weak electrolyte?

Accepted Answer

CH$$_3$$COOH

Question 14

How many moles of oxygen are in 45.0 grams of CaCO$$_3 (MM = 100.1 g/$$mol)?

Accepted Answer

$$45.0 	ext{ g} 	imes \frac{1 	ext{ mol}}{100.1 	ext{ g}} 	imes \frac{3 	ext{ mol O}}{1 	ext{ mol CaCO}_3} = 1.35 	ext{ mol O}$$

Question 15

What is the theoretical yield of Fe (in mol) that can be produced from the reaction of 2.00 mol Fe$$_2O$_3$$ with 3.00 mol CO? $$Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$$

Accepted Answer

3.00 mol CO 	imes \frac{2 	ext{ mol Fe}}{3 	ext{ mol CO}} = 2.00 	ext{ mol Fe}$

Question 16

Which of the following best describes a combination reaction?

Accepted Answer

A reaction in which two or more reactants combine to form a single product.

Question 17

How many moles of CO$$_2$$ are produced when 2.0875 moles of methanol ($$CH_3OH) $$are completely combusted? $$2CH_3OH + 3O_2 \rightarrow 2CO_2 + 4H_2O$$

Accepted Answer

$$2.0875 	ext{ mol CH}_3	ext{OH} 	imes \frac{2 	ext{ mol CO}_2}{2 	ext{ mol CH}_3	ext{OH}} = 2.0875 	ext{ mol CO}_2$$

Question 18

Which of the following is the correct molecular equation for the reaction between H$$_2SO$_4$$ and LiOH?

Accepted Answer

$$H_2SO_4 (aq) + 2LiOH (aq) \rightarrow 2H_2O (l) + Li_2SO_4 (aq)$$

General Chemistry Exam 2 Review: Stoichiometry, Reactions, and Solution Chemistry

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