Chapter 1

A multi-step reaction takes place with the following elementary steps: $\begin{array}{ll}{\text { Step I. }} & {A+B=C} \\ {\text { Step II. }} & {C+A \rightarrow D} \\ {\text { Step III. }} & {C+D \rightarrow B+E}\end{array}$ Why would increasing the temperature make the reaction rate go up? (A) It is an endothermic reaction that needs an outside energy source to function. (B) The various molecules in the reactions will move faster and collide more often. (C) The overall activation energy of the reaction will be lowered. (D) A higher fraction of molecules will have the same activation energy.

Choose the correct net ionic equation representing the reaction that occurs when solutions of potassium carbonate and copper (I) chloride are mixed. (A) \(\mathrm{K}_{2} \mathrm{CO}_{3}(a q)+2 \mathrm{CuCl}(a q) \rightarrow 2 \mathrm{KCl}(a q)+\mathrm{Cu}_{2} \mathrm{CO}_{3}(s)\) (B) \(\mathrm{K}_{2} \mathrm{CO}_{3}(a q)+2 \mathrm{CuCl}(a q) \rightarrow 2 \mathrm{KCl}(\mathrm{s})+\mathrm{Cu}_{2} \mathrm{CO}_{3}(a q)\) (C) \(\mathrm{CO}_{3}^{2-}+2 \mathrm{Cu}^{+} \rightarrow \mathrm{Cu}_{2} \mathrm{CO}_{3}\) (D) \(\mathrm{CO}_{3}^{2-}+\mathrm{Cu}^{2+} \rightarrow \mathrm{CuCO}_{3}(s)\)

Directions: Questions 4-7 are short free-response questions that require about 9 minutes each to answer and are worth 4 points each. Write your response in the space provided following each question. Examples and equations may be included in your responses where appropriate. For calculations, clearly show the method used and the steps involved in arriving at your answers. You must show your work to receive credit for your answer. Pay attention to significant figures. Hyprobromous acid, HBrO, is a weak monoprotic acid with a \(K_{\mathrm{a}}\) value of \(2.0 \times 10^{-9} \mathrm{at} 25^{\circ} \mathrm{C} .\) (a) Write out the equilibrium reaction of hyprobromous acid with water, identifying any conjugate acid/based pairs present. (b) (i) What would be the percent dissociation of a 0.50 M solution of hyprobromous acid? (ii) If the 0.50 M solution were diluted, what would happen to the percent dissociation of the HBrO? Why?

A strip of metal \(\mathrm{X}\) is placed into a solution containing \(\mathrm{Y}^{2+}\) ions and no reaction occurs. When metal \(\mathrm{X}\) is placed in a separate solution containing \(\mathrm{Z}^{2+}\) ions, metal \(\mathrm{Z}\) starts to form on the strip. Which of the following choices organizes the reduction potentials for metals \(\mathrm{X}, \mathrm{Y},\) and \(\mathrm{Z}\) from greatest to least? (A) \(\quad \mathrm{X}>\mathrm{Y}>\mathrm{Z}\) (B) \(\quad \mathrm{Y}>\mathrm{Z}>\mathrm{X}\) (C) \(\quad \mathrm{Z}>\mathrm{X}>\mathrm{Y}\) (D) \(\mathrm{Y}>\mathrm{X}>\mathrm{Z}\)

A student titrates 20.0 \(\mathrm{mL}\) of 1.0 \(M \mathrm{NaOH}\) with 2.0 \(\mathrm{M}\), \(\mathrm{HCO}_{2} \mathrm{H}\left(K_{\mathrm{a}}=1.8 \times 10^{-4}\right) .\) Formic acid is a monoprotic acid. \(\mathrm{CH}_{3} \mathrm{NH}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \leftrightarrow \mathrm{OH}^{-}(a q)+\mathrm{CH}_{3} \mathrm{NH}_{3}^{+}(a q)\) The above equation represents the reaction between the base methylamine \(\left(K_{\mathrm{b}}=4.38 \times 10^{-4}\right)\) and water. Which of the following best represents the.concentrations of the various species at equilibrium? (A) \(\left[\mathrm{OH}^{-}\right]>\left[\mathrm{CH}_{3} \mathrm{NH}_{2}\right]=\left[\mathrm{CH}_{3} \mathrm{NH}_{3}^{+}\right]\) (B) \(\left[\mathrm{OH}^{-}\right]=\left[\mathrm{CH}_{3} \mathrm{NH}_{2}\right]=\left[\mathrm{CH}_{3} \mathrm{NH}_{3}^{+}\right]\) (C) \(\left[\mathrm{CH}_{3} \mathrm{NH}_{2}\right]>\left[\mathrm{OH}^{-}\right]>\left[\mathrm{CH}_{3} \mathrm{NH}_{3}^{+}\right]\) (D) \(\left[\mathrm{CH}_{3} \mathrm{NH}_{2}\right]>\left[\mathrm{OH}^{-}\right]=\left[\mathrm{CH}_{3} \mathrm{NH}_{3}+\right]\)

Why does an ion of phosphorus, \(\mathrm{P}^{3-}\) , have a larger radius than a neutral atom of phosphorus? (A) There is a greater Coulombic attraction between the nucleus and the electrons in \(\mathrm{P}^{3}\) . (B) The core electrons in \(\mathrm{P}^{3-}\) exert a weaker shielding force than those of a neutral atom. (C) The nuclear charge is weaker in \(\mathrm{P}^{3-}\) than it is in P. (D) The electrons in \(\mathrm{P}^{3-}\) have a greater Coulombic repulsion than those in the neutral atom.

$$\mathrm{SO}_{2} \mathrm{Cl}_{2} \rightarrow \mathrm{SO}_{2}(g)+\mathrm{Cl}_{2}(g)$$ At \(600 \mathrm{K}, \mathrm{SO}_{2} \mathrm{Cl}_{2}\) will decompose to form sulfur dioxide and chlorine gas via the above equation. If the reaction is found to be first order overall, which of the following will cause an increase in the half life of \(\mathrm{SO}_{2} \mathrm{Cl}_{2} ?\) (A) Increasing the initial concentration of \(\mathrm{SO}_{2} \mathrm{Cl}_{2}\) (B) Increasing the temperature at which the reaction occurs (C) Decreasing the overall pressure in the container (D) None of these will increase the half life.

$2 \mathrm{ClF}(g)+\mathrm{O}_{2}(g) \leftrightarrow \mathrm{Cl}_{2} \mathrm{O}(g)+\mathrm{F}_{2} \mathrm{O}(g) \Delta H=167 \mathrm{kJ} / \mathrm{mol}_{\mathrm{rxn}}$ During the reaction above, the product yield can be increased by increasing the temperature of the reaction. Why is this effective? (A) The reaction is endothermic; therefore adding heat will shift it to the right. (B) Increasing the temperature increases the speed of the molecules, meaning there will be more collisions between them. (C) The reactants are less massive than the products, and an increase in temperature will cause their kinetic energy to increase more than that of the products. (D) The increase in temperature allows for a higher percentage of molecular collisions to occur with the proper orientation to create the product.

Which of the following is true for an endothermic reaction? (A) The strength of the bonds in the products exceeds the strength of the bonds in the reactants. (B) The activation energy is always greater than the activation energy for an exothermic reaction. (C) Energy is released over the course of the reaction. (D) A catalyst will increase the rate of the reaction by increasing the activation energy.

$$A+B \rightarrow C+D \quad \text { rate }=k[A][B]^{2}$$ What are the potential units for the rate constant for the above reaction? (A) \(\mathrm{s}^{-1}\) (B) \(\mathrm{s}^{-1} M^{-1}\) (C) \(\mathrm{s}^{-1} M^{-2}\) (D) \(\mathrm{s}^{-1} M^{-3}\)