Chapter 1

$$A+B \rightarrow C+D \quad \text { rate }=k[A][B]^{2}$$ 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) \(\mathrm{s}^{-1} M^{-3}\)

Which neutral atom of the following elements would have the most unpaired electrons? (A) Titanium (B) Manganese (C) Nickel (D) Zinc

A sample of liquid \(\mathrm{NH}_{3}\) is brought to its boiling point. Which of the following occurs during the boiling process? (A) The N-H bonds within the NH_{3} \text { molecules break apart. } (B) The overall temperature of the solution rises as the NH, molecules speed up. (C) The amount of energy within the system remains constant. (D) The hydrogen bonds holding separate \(\mathrm{NH}_{3}\) molecules together break apart.

\(2 \mathrm{Al}(s)+3 \mathrm{Cl}_{2}(g) \rightarrow 2 \mathrm{AlCl}_{3}(s)\) The reaction above is not thermodynamically favored under standard conditions, but it becomes thermodynamically favored as the temperature decreases toward absolute zero. Which of the following is true at standard conditions? (A) \(\Delta S\) and \(\Delta H\) are both negative. (B) \(\Delta S\) and \(\Delta H\) are both positive. (C) \(\Delta S\) is negative, and \(\Delta H\) is positive. (D) \(\Delta S\) is positive, and \(\Delta H\) is negative.

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.

Which gas particles have a higher RMS velocity and why? (A) Hydrogen, because it has a lower molar mass (B) Neon, because it has a higher molar mass (C) Hydrogen, because it has a larger atomic radius (D) Neon, because it has a smaller atomic radius

The following mechanism is proposed for a reaction: \(\begin{array}{ll}{2 \mathrm{A} \rightarrow \mathrm{B}} & {\text { (fast equilibrium) }} \\ {\mathrm{C}+\mathrm{B} \rightarrow \mathrm{D}} & {\text { (slow) }} \\ {\mathrm{D}+\mathrm{A} \rightarrow \mathrm{E}} & {\text { (fast) }}\end{array}\) Which of the following is the correct rate law for compete reaction? (A) Rate \(=k[\mathrm{C}]^{2}[\mathrm{B}]\) (B) Rate \(=k\left[\mathrm{Cl}[\mathrm{A}]^{2}\right.\) (C) Rate \(=k[\mathrm{C}][\mathrm{A}]^{3}\) (D) Rate \(=k[\mathrm{D}][\mathrm{A}]\)

In which of the following compounds is the oxidation number of chromium the greatest? (A) \(\mathrm{CrO}_{4} 2^{-}\) (B) \(\mathrm{CrO}\) (C) \(\mathrm{Cr}^{3+}\) (D) \(\operatorname{Cr}(s)\)

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. A stock solution of \(2.0 \mathrm{M} \mathrm{MgCl}_{2}\) is dissolved in water. (a) (i) In the beaker below, draw a particulate diagram that represents \(\mathrm{MgCl}_{2}\) dissolved in water. The approximate sizes of each atom/ion are provided for you. Your diagram should include at least four water molecules, which should be correctly oriented compared to the ions dissolved in solution. (DIAGRAM CANT COPY) (ii) Why are the chloride ions from (a)(i) larger than the magnesium (b) (i) A student wishes to make up 500 \(\mathrm{mL}\) of 0.50 \(M \mathrm{MgCl}_{2}\) for an experiment. Explain the best method of doing so utilizing a graduated cylinder and a volumetric flask. Assume \(\mathrm{MgCl}_{2}\) is fully soluble. (ii) What are the concentrations of the \(\mathrm{Mg}^{2+}\) and \(\mathrm{Cl}^{-}\) ions in the new solution?

The following reaction is found to be at equilibrium at 25°C: \(2 \mathrm{SO}_{3}(g) \leftrightarrow \mathrm{O}_{2}(g)+2 \mathrm{SO}_{2}(g) \quad \Delta H=-198 \mathrm{kJ} / \mathrm{mol}\) Which of the following would cause the reverse reaction to speed up? (A) Adding more \(\mathrm{SO}_{3}\) (B) Raising the pressure (C) Lowering the temperature (D) Removing some \(\mathrm{SO}_{2}\)