Q: Given the reaction $$2\ \mathrm{NH}_3(g) \rightarrow \mathrm{N}_2(g) + 3\ \mathrm{H}_2(g)$$, which of the following correctly expresses the rate in terms of the change in concentration of $$\mathrm{NH}_3$$?

$$\text{rate} = -\frac{1}{2}\frac{\Delta[\mathrm{NH}_3]}{\Delta t}$$

Q: For the reaction $$3\ \mathrm{O}_2(g) \rightarrow 2\ \mathrm{O}_3(g)$$, how is the rate of disappearance of $$\mathrm{O}_2$$ related to the rate of appearance of $$\mathrm{O}_3$$?

$$\text{rate} = -\frac{1}{3}\frac{\Delta[\mathrm{O}_2]}{\Delta t} = +\frac{1}{2}\frac{\Delta[\mathrm{O}_3]}{\Delta t}$$

Question 1

Which of the following best explains why the vapor pressure of a solution with strong solute-solvent interactions is lower than predicted by Raoult’s Law?

Accepted Answer

The solute-solvent interactions are stronger than solute-solute and solvent-solvent interactions, making it harder for molecules to escape into the vapor phase.

Question 2

A solution is prepared by dissolving 15.6 g of ethanol (molar mass = 46.07 g/mol) in 625 g of water. If the boiling point elevation constant $$K_b$$ for water is $$0.512\ ^\circ\mathrm{C}\ \mathrm{kg}\ \mathrm{mol}^{-1}$$, what is the boiling point of the solution? (Normal boiling point of water is $$100\ ^\circ\mathrm{C})$$

Accepted Answer

$$100.277\ ^\circ\mathrm{C}$$

Question 3

Which equation correctly represents the osmotic pressure ($$\Pi) of a $$solution containing an ionic solute?

Accepted Answer

$$\Pi = iMRT$$

Question 4

Given the reaction $$2\ \mathrm{NH}_3(g) \rightarrow \mathrm{N}_2(g) + 3\ \mathrm{H}_2(g)$$, which of the following correctly expresses the rate in terms of the change in concentration of $$\mathrm{NH}_3$$?

Accepted Answer

$$	ext{rate} = -\frac{1}{2}\frac{\Delta[\mathrm{NH}_3]}{\Delta t}$$

Question 5

A reaction has the rate law $$	ext{rate} = k[\mathrm{A}]^2. If $$the concentration of $$\mathrm{A} is $$doubled, what happens to the reaction rate?

Accepted Answer

The rate quadruples.

Question 6

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

Accepted Answer

The rate is independent of the concentration of the reactant.

Question 7

In the context of osmosis, what is the primary driving force for the movement of solvent molecules across a semipermeable membrane?

Accepted Answer

A difference in solute concentration between the two sides of the membrane.

Question 8

Given the following initial rates data for a reaction: 
Trial 1: $$[A] = 0.10\ \mathrm{M}$$, Rate $$= 0.14\ \mathrm{M/s}$$
Trial 2: $$[A] = 0.30\ \mathrm{M}$$, Rate $$= 1.26\ \mathrm{M/s}$$
What is the order of the reaction with respect to $$A$$?

Accepted Answer

Second order

Question 9

Which of the following best describes the effect of adding a nonvolatile solute to a solvent on the boiling and freezing points of the solution?

Accepted Answer

The boiling point increases and the freezing point decreases.

Question 10

A reaction is found to be first order in $$A$$ and second order in $$B. $$What is the overall order of the reaction?

Accepted Answer

Third order

Question 11

Which of the following graphs best represents the concentration of a reactant versus time for a zero-order reaction?

Accepted Answer

A straight line with a negative slope.

Question 12

If the rate law for a reaction is $$	ext{rate} = k[\mathrm{A}]^0$$, what will happen to the rate if the concentration of $$\mathrm{A} is $$tripled?

Accepted Answer

The rate will remain the same.

Question 13

Which of the following is NOT a factor that affects the rate constant $$k of a $$reaction?

Accepted Answer

Concentration of reactants

Question 14

A solution of $$\mathrm{Ca($$ClO_3$$)_2} is$$ $$0.085\ \mathrm{M} at$$ $$298\ \mathrm{K}. $$What is the osmotic pressure? ($$R = 0.08206\ \mathrm{L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$}$$, $$i = 3)$$

Accepted Answer

$$6.3\ \mathrm{atm}$$

Question 15

Which of the following best describes the method of initial rates?

Accepted Answer

Measuring the rate of reaction at the very beginning for different initial concentrations to determine the reaction order.

Question 16

For the reaction $$3\ \mathrm{O}_2(g) \rightarrow 2\ \mathrm{O}_3(g)$$, how is the rate of disappearance of $$\mathrm{O}_2$$ related to the rate of appearance of $$\mathrm{O}_3$$?

Accepted Answer

$$	ext{rate} = -\frac{1}{3}\frac{\Delta[\mathrm{O}_2]}{\Delta t} = +\frac{1}{2}\frac{\Delta[\mathrm{O}_3]}{\Delta t}$$

Question 17

Which of the following is a correct statement about the effect of a catalyst on a chemical reaction?

Accepted Answer

A catalyst increases the rate constant $$k by $$providing an alternative pathway with a lower activation energy.

L17: Reaction Rates, Rate Laws, and Colligative Properties: Study Notes

Study Guide - Practice Questions

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