Q: Given the reaction $2Cr(OH)_3 (s) + 2NaClO_3 (aq) + 3H_2O_2 (aq) \rightarrow 2Na^+ (aq) + 2CrO_4^{2-} (aq) + 2Cl^- (aq) + 8H_2O (l)$ with $\Delta H_{rxn} = -240.2\ \mathrm{kJ}$, what is the enthalpy change when 1.00 kg of $Cr(OH)_3$ reacts completely? (Molar mass $Cr(OH)_3 = 99.99\ \mathrm{g/mol}$)

$-1.20 \times 10^3\ \mathrm{kJ}$

Q: Which of the following statements about the effect of a catalyst on a reaction is correct?

A catalyst lowers the activation energy, increasing the reaction rate.

Question 1

Which of the following is the correct balanced equation for the standard enthalpy of formation of sodium acetate trihydrate, $\mathrm{NaC_2H_3O_2 \cdot 3H_2O (s)}$?

Accepted Answer

$\mathrm{Na (s) + 2C (s) + 2H_2 (g) + 2O_2 (g) + 3H_2O (l) \rightarrow NaC_2H_3O_2 \cdot 3H_2O (s)}$

Question 2

Given the reaction $2Cr(OH)_3 (s) + 2NaClO_3 (aq) + 3H_2O_2 (aq) \rightarrow 2Na^+ (aq) + 2CrO_4^{2-} (aq) + 2Cl^- (aq) + 8H_2O (l)$ with $\Delta H_{rxn} = -240.2\ \mathrm{kJ}$, what is the enthalpy change when 1.00 kg of $Cr(OH)_3$ reacts completely? (Molar mass $Cr(OH)_3 = 99.99\ \mathrm{g/mol}$)

Accepted Answer

$-1.20 	imes 10^3\ \mathrm{kJ}$

Question 3

A mixture of $He(g)$ and $Ne(g)$ has a total pressure of $1.00\ \mathrm{atm}$ at $50.0\ \mathrm{L}$ and $0.40\ \mathrm{mol}$ of $He$ and $0.25\ \mathrm{mol}$ of $Ne$. What is the partial pressure of $He$ in the mixture?

Accepted Answer

$0.62\ \mathrm{atm}$

Question 4

The reaction $CH_3COCH_3(aq) + HOCl(aq) \rightarrow CH_3COCH_2Cl(aq) + H_2O(l)$ is catalyzed by $OH^-$ and is first order in $[CH_3COCH_3]$, first order in $[OH^-]$, and zero order in $[HOCl]$. If the initial concentrations of $CH_3COCH_3$ and $HOCl$ are increased by a factor of 2.5 and $[OH^-]$ remains unchanged, by what factor does the rate increase?

Accepted Answer

2.5

Question 5

The following reaction is first order in $[N_2O_5]$ and its rate constant is $3.46 	imes 10^{-5}\ \mathrm{s}^{-1}$ at $20^\circ C$: $2N_2O_5 (g) ightarrow 4NO_2 (g) + O_2 (g)$. What time in minutes would it take for the reaction to consume 99% of the initial amount of $N_2O_5$?

Accepted Answer

$2.22 	imes 10^3$ min

Question 6

For the reaction $A \rightarrow C$ via two steps: $A \rightarrow B$ (slow), $B \rightarrow C$ (fast), which of the following statements is correct?

Accepted Answer

The rate-determining step is $A \rightarrow B$.

Question 7

Consider the reversible reaction: $HSO_4^- (aq) + H_2O (l) \rightleftharpoons SO_4^{2-} (aq) + H_3O^+ (aq)$ with $\Delta H_{rxn} > 0$. If the temperature is increased, in which direction will the equilibrium shift?

Accepted Answer

Right

Question 8

Which of the following is the correct expression for the equilibrium constant $K$ for the reaction $HSO_4^- (aq) + H_2O (l) \rightleftharpoons SO_4^{2-} (aq) + H_3O^+ (aq)$?

Accepted Answer

$K = \dfrac{[SO_4^{2-}][H_3O^+]}{[HSO_4^-]}$

Question 9

Which of the following pairs is a correct conjugate acid-base pair for the reaction $HSO_4^- (aq) + H_2O (l) \rightarrow SO_4^{2-} (aq) + H_3O^+ (aq)$?

Accepted Answer

$HSO_4^-$ / $SO_4^{2-}$

Question 10

Rank the following in order of increasing acid strength: $H_2SO_4$, $HNO_3$, $HClO_4$.

Accepted Answer

$HNO_3 < H_2SO_4 < HClO_4$

Question 11

Which of the following solutions has the lowest pH?

Accepted Answer

$0.010\ \mathrm{M}\ HCl$

Question 12

Calculate the pH of a $0.050\ \mathrm{M}\ HBr(aq)$ solution. ($pK_a(HBr) = -9$ at $25^\circ C$)

Accepted Answer

1.30

Question 13

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

Accepted Answer

A catalyst lowers the activation energy, increasing the reaction rate.

Question 14

Which of the following salts will produce a basic solution when dissolved in water?

Accepted Answer

$Na_2CO_3$

Question 15

Which of the following has the highest entropy of vaporization?

Accepted Answer

$CH_3OH$

Question 16

Which of the following is the strongest acid?

Accepted Answer

$HClO_4$

Question 17

Which of the following is the correct rate law for a reaction that is first order in $A$ and second order in $B$?

Accepted Answer

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

Question 18

Which of the following will increase the rate of a chemical reaction?

Accepted Answer

Increasing the temperature

Question 19

Which of the following is the correct expression for the Arrhenius equation?

Accepted Answer

$k = A e^{-E_a/(RT)}$

General Chemistry Exam 3 Study Guide: Thermochemistry, Chemical Kinetics, Equilibrium, and Acids/Bases

Study Guide - Practice Questions

Study Guide - Flashcards