Q: A solution is prepared by dissolving 10.0 g of NaCl (molar mass = 58.44 g/mol) in 500.0 g of water. What is the molality ($$m) of $$the solution?

$$m = \frac{10.0}{58.44} \div 0.500 = 0.342\ \text{mol/kg}$$

Q: A solution is made by dissolving 5.00 g of glucose (C$$_6H$_{12}O$_6$$, molar mass = 180.16 g/mol) in enough water to make 100.0 mL of solution. What is the molarity ($$M) of $$the solution?

$$M = \frac{5.00/180.16}{0.1000} = 0.278\ \text{mol/L}$$

Q: A reaction is found to be second order overall. Which of the following could be the correct units for the rate constant $$k$$?

$$\text{L·mol}^{-1}\text{s}^{-1}$$

Question 1

Which of the following pairs of substances would you expect to form an ideal solution based on the 'like dissolves like' principle?

Accepted Answer

Hexane (nonpolar) and heptane (nonpolar)

Question 2

A solution is prepared by dissolving 10.0 g of NaCl (molar mass = 58.44 g/mol) in 500.0 g of water. What is the molality ($$m) of $$the solution?

Accepted Answer

$$m = \frac{10.0}{58.44} \div 0.500 = 0.342\ 	ext{mol/kg}$$

Question 3

Which of the following statements best describes a positive deviation from Raoult’s law?

Accepted Answer

The vapor pressure of the solution is higher than predicted due to weak solute–solvent interactions.

Question 4

According to Henry’s law, how does the solubility of a gas in a liquid change with increasing pressure?

Accepted Answer

It increases.

Question 5

A solution contains 2.0 mol of ethanol and 8.0 mol of water. What is the mole fraction ($$\chi) of $$ethanol?

Accepted Answer

$$\chi = \frac{2.0}{2.0 + 8.0} = 0.20$$

Question 6

Which colligative property explains why adding salt to icy roads helps melt the ice?

Accepted Answer

Freezing point depression

Question 7

A solution is made by dissolving 5.00 g of glucose (C$$_6H$_{12}O$_6$$, molar mass = 180.16 g/mol) in enough water to make 100.0 mL of solution. What is the molarity ($$M) of $$the solution?

Accepted Answer

$$M = \frac{5.00/180.16}{0.1000} = 0.278\ 	ext{mol/L}$$

Question 8

Which of the following best describes an unsaturated solution?

Accepted Answer

It contains less solute than the maximum amount that can dissolve at a given temperature.

Question 9

Which of the following equations correctly expresses the relationship for boiling point elevation?

Accepted Answer

$$\Delta T_b = K_b m i$$

Question 10

A reaction has the following rate law: $$	ext{rate} = k[	ext{A}]^2[	ext{B}]. If $$the concentration of A is doubled and B is halved, how does the rate change?

Accepted Answer

The rate increases by a factor of 2.

Question 11

Which of the following is true for a first-order reaction?

Accepted Answer

A plot of $$\ln[A] vs. $$time is linear.

Question 12

Given the reaction $$2	ext{NO}_2 ightarrow 2	ext{NO} + 	ext{O}_2$$, if the rate of disappearance of NO$$_2 is$$ $$0.10\ 	ext{mol/L·s}$$, what is the rate of appearance of O$$_2$$?

Accepted Answer

$$0.05\ 	ext{mol/L·s}$$

Question 13

Which factor does NOT affect the rate constant ($$k) of a $$reaction?

Accepted Answer

Concentration of reactants

Question 14

The Arrhenius equation is given by $$k = Ae$$^{-E_a/(RT)}$$. Which of the following changes will increase the rate constant k$?

Accepted Answer

Increasing the temperature

Question 15

Which of the following best describes a catalyst in a reaction mechanism?

Accepted Answer

It is present at the start, consumed in one step, and regenerated in a later step.

Question 16

A reaction is found to be second order overall. Which of the following could be the correct units for the rate constant $$k$$?

Accepted Answer

$$	ext{L·mol}^{-1}	ext{s}^{-1}$$

Question 17

Which of the following is a correct expression for the mole fraction ($$\chi) of $$solute in a solution?

Accepted Answer

$$\chi = \frac{	ext{amount solute (in mol)}}{	ext{total amount of solute and solvent (in mol)}}$$

Question 18

If a reaction mechanism has a slow first step, how is the rate law determined?

Accepted Answer

It is based directly on the slow step.

Question 19

Which of the following best describes the effect of increasing temperature on the rate of a chemical reaction, according to collision theory?

Accepted Answer

It increases the number of collisions with sufficient energy to react.

Solutions and Chemical Kinetics: Exam 2 Study Guide

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