Question 1

A solution is prepared by dissolving 0.50 mol of NaCl in 1.0 kg of water. What is the boiling point elevation of the solution? ($$K_b$$ for water = $$0.512 \ \mathrm{^	ext{o}C \cdot kg \cdot $$mol^{-1}$$})$$

Accepted Answer

$$1.02 \ \mathrm{^	ext{o}C}$$

Question 2

Which of the following statements best explains why the freezing point of seawater is lower than that of pure water?

Accepted Answer

Dissolved salts disrupt the formation of the solid lattice, lowering the freezing point.

Question 3

A 0.1 M solution of glucose ($$C_6H_{12}O_6$) and a 0.1 M solution of NaCl are prepared. Which solution will have a higher osmotic pressure at the same temperature?

Accepted Answer

NaCl solution, because it dissociates into two ions.

Question 4

Which of the following is the correct integrated rate law for a first-order reaction?

Accepted Answer

$$\ln [A] = -kt + \ln [A]_0$$

Question 5

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

Accepted Answer

4

Question 6

Which of the following best describes the role of a catalyst in a chemical reaction?

Accepted Answer

It provides an alternative pathway with lower activation energy.

Question 7

The half-life of a second-order reaction is given by which of the following equations?

Accepted Answer

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

Question 8

A student mixes equal moles of $$Na_2SO_4$$, $$CaCl_2$$, $$KNO_3$$, and $$MgSO_4 in $$equal masses of water. Which solution will have the highest boiling point?

Accepted Answer

$$Na_2SO_4$$

Question 9

The rate constant for the dissolution of oxygen gas in water at 25°C is $$k_H = 0.031 \ \mathrm{mol \cdot L$$^{-1}$$ \cdot $$atm^{-1}$$}. If $$the partial pressure of oxygen is 0.21 atm, what is the concentration of dissolved oxygen?

Accepted Answer

$$0.00651 \ \mathrm{mol \cdot L$$^{-1}$$}$$

Question 10

A reaction is found to have the following rate law: $$	ext{rate} = k[NO][O_3$][Cl^-]. $$What are the units of the rate constant, k, for this rate law?

Accepted Answer

$$\mathrm{M$$^{-2}$$ \cdot s$$^{-1}$$}$$

Question 11

An experiment is performed in which the concentration of a reactant is measured as a function of time. The plot of concentration versus time results in a curved line. Which of the following is the most accurate conclusion from this information?

Accepted Answer

The reaction is not zero order.

Question 12

At 50°C, a reaction is found to be second order in the reactant, $$NO_2$$, with a rate constant, $$k$$, of $$4.33 	imes 10$$^{-4}$$ \ \mathrm{M$$^{-1}$$ \cdot s$$^{-1}$$}. An $$experiment is performed at 50°C in which the initial concentration of $$NO_2 is$$ $$0.030 \ \mathrm{M}. $$What is the concentration of $$NO_2$$ after the reaction proceeds for 90 seconds?

Accepted Answer

$$0.018 \ \mathrm{M}$$

Question 13

Consider the reaction: $$N_2 + 3H_2$$ \rightarrow 2NH_3$$. At a particular moment in time, it is observed that hydrogen gas is being consumed by the reaction at a rate of 0.210$$ \ \mathrm{M/s}$$. At the same moment in time, at what rate is NH_3$ being produced?

Accepted Answer

$$0.140 \ \mathrm{M/s}$$

Question 14

A first order reaction is found to have a half-life of 10 minutes. How long will it take for 75% of the reactant to be used up?

Accepted Answer

20 min

Question 15

A reaction is found to have a rate constant of $$0.0054 \ \mathrm{s$$^{-1}$$} at 200K $$and a rate constant of $$0.0081 \ \mathrm{s$$^{-1}$$} at 250K. $$What is the activation energy of this reaction?

Accepted Answer

$$11.3 \ \mathrm{kJ/mol}$$

Question 16

Many biochemical reactions involve enzymes. Which of the following roles does an enzyme play in these reactions?

Accepted Answer

Catalyst

Question 17

For the reaction $$2A + B \rightarrow C + 3D$$, the following data is collected from a series of experiments all performed at 25°C. Which is the correct rate law for this reaction?

Accepted Answer

rate = $$k[A]^2[B]$$

Question 18

Based on the mechanism and the energy diagram for the reaction $$2A + 2B \rightarrow C$$, what is the overall rate law for this reaction?

Accepted Answer

rate = $$k[A]^2[B]$$

Question 19

Which substances are intermediates in a reaction mechanism involving steps $$A \rightarrow X$$, $$X \rightarrow Y$$, $$Y \rightarrow B$$?

Accepted Answer

X and Y

Question 20

Which points on an energy diagram represent transition states?

Accepted Answer

2, 4, and 6

Question 21

Is the reaction exothermic or endothermic? And which two points on the energy diagram do you use to determine that?

Accepted Answer

Exothermic, 1 and 7

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