Q: A solution is prepared by dissolving 0.5 mol of NaCl in 1.0 kg of water. Using the van’t Hoff factor ($$i) $$for NaCl, which is approximately 2, calculate the freezing point depression ($$\Delta T_f) if $$the freezing point depression constant ($$K_f) $$for water is $$1.86\ \mathrm{K\ kg\ $$mol^{-1}$$}. $$Which is the correct value?

$$\Delta T_f = 1.86\ \mathrm{K\ kg\ $$mol^{-1}$$} \times 0.5\ \mathrm{mol} \times 2 = 1.86 K$$

Q: A student measures the equilibrium concentrations of $$A$$, $$B$$, and $$C$$ for the reaction $$A + 2B \rightleftharpoons 3C as$$ $$[A] = 0.2\ \mathrm{M}$$, $$[B] = 0.1\ \mathrm{M}$$, and $$[C] = 0.5\ \mathrm{M}. $$What is the value of $$K_c$$?

$$K_c = \frac{[C]^3}{[A][B]^2} = \frac{(0.5)^3$}{0.2 \times (0.1)^2$} = 62.5$$

Question 1

Which of the following best describes the effect of adding a nonvolatile solute to a solvent on its vapor pressure?

Accepted Answer

The vapor pressure of the solvent decreases according to Raoult's law.

Question 2

A solution is prepared by dissolving 0.5 mol of NaCl in 1.0 kg of water. Using the van’t Hoff factor ($$i) $$for NaCl, which is approximately 2, calculate the freezing point depression ($$\Delta T_f) if $$the freezing point depression constant ($$K_f) $$for water is $$1.86\ \mathrm{K\ kg\ $$mol^{-1}$$}. $$Which is the correct value?

Accepted Answer

$$\Delta T_f = 1.86\ \mathrm{K\ kg\ $$mol^{-1}$$} 	imes 0.5\ \mathrm{mol} 	imes 2 = 1.86 K$$

Question 3

Which equation is used to calculate the osmotic pressure ($$\Pi) of a $$dilute solution?

Accepted Answer

$$\Pi = iMRT$$

Question 4

A student wants to estimate the boiling point elevation of a solution. Which formula should they use?

Accepted Answer

$$\Delta T_b = i K_b m$$

Question 5

Which factor does NOT affect the rate of a chemical reaction?

Accepted Answer

Color of the reactants

Question 6

For a first-order reaction, which of the following correctly expresses the relationship between concentration and time?

Accepted Answer

$$[A]_t = [A]_0 e$$^{-kt}$$

Question 7

Which statement about the Arrhenius equation is correct?

Accepted Answer

It relates the rate constant to the activation energy and temperature.

Question 8

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

Accepted Answer

12

Question 9

Which of the following is true about catalysts?

Accepted Answer

Catalysts provide an alternative pathway with lower activation energy.

Question 10

Which integrated rate law would you use to determine the half-life of a second-order reaction?

Accepted Answer

$$t_{1/2} = \frac{1}{k[A]_0}$$

Question 11

Which of the following is the correct equilibrium constant expression ($$K_c) $$for the reaction: $$2A + B \rightleftharpoons 3C$$?

Accepted Answer

$$K_c = \frac{[C]^3}{[A]^2[B]}$$

Question 12

If the equilibrium constant $$K_c$$ for a reaction is much greater than 1, what does this indicate about the reaction at equilibrium?

Accepted Answer

Products are favored.

Question 13

Which of the following will NOT change the value of the equilibrium constant ($$K) $$for a given reaction?

Accepted Answer

Adding a catalyst

Question 14

For the reaction $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$, which of the following changes will shift the equilibrium toward the products?

Accepted Answer

Increasing the concentration of $$N_2$$

Question 15

A solution of glucose ($$C_6H_{12}O_6$) in water has a molality of 0.2$$\ \mathrm{mol\ $$kg^{-1}$$}$$. If glucose does not dissociate, what is the expected van’t Hoff factor (i$) for this solution?

Accepted Answer

1

Question 16

Which statement best describes the difference between $$K_c$$ and $$K_p$$ for a chemical equilibrium?

Accepted Answer

$$K_c is $$based on concentrations, $$K_p is $$based on partial pressures.

Question 17

Which of the following is a correct statement about zero-order reactions?

Accepted Answer

The rate is independent of the concentration of reactants.

Question 18

A reaction mechanism consists of two steps: Step 1 (slow): $$A + B \rightarrow C$$, Step 2 (fast): $$C + D \rightarrow E. $$What is the rate-determining step?

Accepted Answer

Step 1

Question 19

Which of the following is the correct expression for the equilibrium constant for the reaction $$CaCO_3(s$$) \rightleftharpoons CaO(s) + $$CO_2(g$$)$$?

Accepted Answer

$$K = [CO_2$]$$

Question 20

A student measures the equilibrium concentrations of $$A$$, $$B$$, and $$C$$ for the reaction $$A + 2B \rightleftharpoons 3C as$$ $$[A] = 0.2\ \mathrm{M}$$, $$[B] = 0.1\ \mathrm{M}$$, and $$[C] = 0.5\ \mathrm{M}. $$What is the value of $$K_c$$?

Accepted Answer

$$K_c = \frac{[C]^3}{[A][B]^2} = \frac{(0.5)^3$}{0.2 	imes (0.1)^2$} = 62.5$$

General Chemistry Study Notes: Colligative Properties, Chemical Kinetics, and Chemical Equilibrium

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