Q: A solution is prepared by dissolving 14.0 g of NaCl in enough water to make 100 g of solution. What is the mass percent of NaCl in the solution?

$$\text{Mass percent} = \frac{14.0\,\text{g}}{100\,\text{g}} \times 100\% = 14.0\%$$

Q: How many mL of 15.0 M NaOH are needed to make 100.0 mL of 3.00 M NaOH?

$$V_1$$ = \frac{$$M_2$$ $$V_2$$}{$$M_1$$} = \frac{3.00 \times 100.0}{15.0} = 20.0\,\text{mL}$$

Q: A 250.0 mL solution contains 90.0 g of ammonium dichromate, $$(NH_4$)_2Cr_2O_7 ($$molar mass = 252.10 g/mol). What is the molarity of the solution?

$$M = \frac{90.0\,\text{g}}{252.10\,\text{g/mol}} \div 0.2500\,\text{L} = 1.43\,\text{M}$$

Question 1

Which of the following best describes a homogeneous mixture, as shown in the study materials?

Accepted Answer

A mixture with a uniform composition throughout, such as tea with sugar.

Question 2

A solution is prepared by dissolving 14.0 g of NaCl in enough water to make 100 g of solution. What is the mass percent of NaCl in the solution?

Accepted Answer

$$	ext{Mass percent} = \frac{14.0\,	ext{g}}{100\,	ext{g}} 	imes 100\% = 14.0\%$$

Question 3

Which of the following statements about electrolytes is correct?

Accepted Answer

Strong electrolytes completely ionize in water and conduct electricity well.

Question 4

A chemist wants to prepare 1.00 L of a 1.00 M NaCl solution. Which of the following steps is correct?

Accepted Answer

Weigh out 58.44 g of NaCl, dissolve in less than 1 L of water, then add water to the 1 L mark.

Question 5

Which equation correctly relates the concentrations and volumes before and after dilution?

Accepted Answer

$$M_1$$ $$V_1$$ = $$M_2$$ $$V_2$$

Question 6

How many mL of 15.0 M NaOH are needed to make 100.0 mL of 3.00 M NaOH?

Accepted Answer

$$V_1$$ = \frac{$$M_2$$ $$V_2$$}{$$M_1$$} = \frac{3.00 	imes 100.0}{15.0} = 20.0\,	ext{mL}$$

Question 7

Which of the following is a correct net ionic equation for the precipitation reaction between KOH(aq) and Mg(NO$$_3$$)$$_2(aq$$)?

Accepted Answer

$$\mathrm{Mg$$^{2+}$$ (aq) + 2OH^- (aq) \rightarrow Mg(OH)_2 (s)}$$

Question 8

A 250.0 mL solution contains 90.0 g of ammonium dichromate, $$(NH_4$)_2Cr_2O_7 ($$molar mass = 252.10 g/mol). What is the molarity of the solution?

Accepted Answer

$$M = \frac{90.0\,	ext{g}}{252.10\,	ext{g/mol}} \div 0.2500\,	ext{L} = 1.43\,	ext{M}$$

Question 9

Which of the following best explains why the total volume of a solution is not always the sum of the volumes of solute and solvent added together?

Accepted Answer

Solute and solvent particles interact and occupy less space when mixed.

Question 10

Which of the following compounds is most likely to be a strong electrolyte in water?

Accepted Answer

NaCl

Question 11

Which of the following is the correct balanced molecular equation for the reaction between potassium carbonate and nickel(II) chloride?

Accepted Answer

$$\mathrm{K_2CO_3 (aq) + $$NiCl_2$$ (aq) \rightarrow 2KCl (aq) + $$NiCO_3$$ (s)}$$

Question 12

A solution is labeled as 25.6% ethanol (v/v). What does this mean?

Accepted Answer

There are 25.6 mL of ethanol in every 100 mL of solution.

Question 13

Which of the following is a correct statement about the dissolution of ionic compounds in water?

Accepted Answer

Ions are separated and surrounded by water molecules, which insulate them from each other.

Question 14

Which of the following is a spectator ion in the reaction: $$2\mathrm{KOH} (aq) + \mathrm{Mg(NO_3$)_2} (aq) \rightarrow 2\mathrm{$$KNO_3$$} (aq) + \mathrm{Mg(OH)_2} (s)$$?

Accepted Answer

$$\mathrm{K^+}$$

Question 15

Which of the following best describes the difference between a pure compound and a homogeneous mixture?

Accepted Answer

A pure compound has a fixed composition; a homogeneous mixture has variable composition.

Question 16

What is the maximum mass (theoretical yield) of PbCl$$_2$$ that can be made from the complete reaction of 0.150 L of 0.175 M Pb(NO$$_3$$)$$_2$$? (Molar mass PbCl$$_2 = 278.1 g/$$mol)

Accepted Answer

$$0.150\,	ext{L} 	imes 0.175\,	ext{mol/L} 	imes 278.1\,	ext{g/mol} = 7.30\,	ext{g}$$

Reactions in Aqueous Solutions and Solution Chemistry

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