Question 1

Which of the following best describes the difference between a strong electrolyte and a weak electrolyte in aqueous solution?

Accepted Answer

A strong electrolyte completely dissociates into ions, while a weak electrolyte only partially dissociates.

Question 2

A 0.10 M solution of acetic acid ($$\mathrm{CH_3COOH}) $$has a measured pH of 2.87. Which equation would you use to calculate the acid dissociation constant ($$K_a) $$for acetic acid?

Accepted Answer

$$K_a = \frac{[\mathrm{H^+}][\mathrm{CH_3COO^-}]}{[\mathrm{CH_3COOH}]}$$

Question 3

Which of the following statements about the solubility product constant ($$K_{sp}) is $$correct?

Accepted Answer

$$K_{sp} is $$the equilibrium constant for the dissolution of a sparingly soluble ionic compound.

Question 4

A student mixes 100 mL of 0.10 M $$\mathrm{NaCl}$$ with 100 mL of 0.10 M $$\mathrm{$$AgNO_3$$}. $$What is the net ionic equation for the reaction that occurs?

Accepted Answer

$$\mathrm{Ag^+} (aq) + \mathrm{Cl^-} (aq) \rightarrow \mathrm{AgCl} (s)$$

Question 5

Which of the following is the correct expression for the equilibrium constant ($$K_c) $$for the reaction $$\mathrm{N_2$} (g) + 3\mathrm{H_2$} (g) \rightleftharpoons 2\mathrm{NH_3$} (g)$$?

Accepted Answer

$$K_c = \frac{[\mathrm{NH_3$}]^2}{[\mathrm{N_2$}][\mathrm{H_2$}]^3}$$

Question 6

A buffer solution is prepared by mixing equal concentrations of acetic acid ($$\mathrm{CH_3COOH}) $$and sodium acetate ($$\mathrm{CH_3COONa}). $$Which equation would you use to calculate the pH of this buffer?

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log \left( \frac{[\mathrm{CH_3COO^-}]}{[\mathrm{CH_3COOH}]} \right)$$

Question 7

Which of the following best explains why increasing the temperature generally increases the rate of a chemical reaction?

Accepted Answer

Higher temperature increases the kinetic energy of molecules, leading to more frequent and energetic collisions.

Question 8

A reaction has a rate law: $$	ext{Rate} = k[\mathrm{NO_2$}]^2. If $$the concentration of $$\mathrm{NO_2$} is $$doubled, by what factor does the rate increase?

Accepted Answer

The rate increases by a factor of 4.

Question 9

Which of the following is the correct equation for calculating the change in Gibbs free energy ($$\Delta G) at $$constant temperature?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 10

A solution is prepared by dissolving 0.50 mol of $$\mathrm{Na_2SO_4} in $$enough water to make 1.0 L of solution. What is the concentration of $$\mathrm{SO_4$^{2-}}$$ ions?

Accepted Answer

0.50 M

Question 11

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

A catalyst lowers the activation energy, increasing the rate of the reaction without being consumed.

Question 12

Which of the following is the correct equation for the first law of thermodynamics?

Accepted Answer

$$\Delta E = q + w$$

Question 13

A student titrates 25.0 mL of 0.100 M $$\mathrm{HCl}$$ with 0.100 M $$\mathrm{NaOH}. $$What is the pH at the equivalence point?

Accepted Answer

7.0

Question 14

Which of the following is the correct equation for the relationship between the equilibrium constant ($$K) $$and the standard Gibbs free energy change ($$\Delta G^\circ$$)?

Accepted Answer

$$\Delta G^\circ = -RT \ln K$$

Question 15

Which of the following is the correct equation for calculating the osmotic pressure ($$\Pi) of a $$solution?

Accepted Answer

$$\Pi = MRT$$

Question 16

Which of the following best explains why salt is used to melt ice on roads in winter?

Accepted Answer

Salt lowers the freezing point of water by disrupting the equilibrium between solid and liquid phases.

Question 17

Which of the following is the correct equation for the rate constant ($$k) of a $$reaction as a function of temperature according to the Arrhenius equation?

Accepted Answer

$$k = A e$$^{-\frac{E_a}$${RT}}$$

Question 18

A reaction mixture contains 0.20 M $$\mathrm{A}$$ and 0.30 M $$\mathrm{B} at $$equilibrium. The equilibrium constant for the reaction $$\mathrm{A} + \mathrm{B} \rightleftharpoons \mathrm{C} is$$ $$K_c = 2.0. $$What is the concentration of $$\mathrm{C} at $$equilibrium?

Accepted Answer

0.12 M

Question 19

Which of the following is the correct equation for the Henry's law constant ($$k_H) $$relating the solubility of a gas to its partial pressure?

Accepted Answer

$$C = k_H P$$

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