Practice Test 3 - AP Chemistry

20 questions. Answer them in any order, then submit to see your score and every explanation.

Excess solid copper(I) chloride, $\text{CuCl}(s)$ , is placed in pure water at $25^\circ\text{C}$ until equilibrium is established. The $K_{sp}$ of $\text{CuCl}$ is $1.0\times10^{-6}$ . Dissolution: $\text{CuCl}(s)\rightleftharpoons \text{Cu}^+(aq)+\text{Cl}^-(aq)$ Starting with zero ion concentrations, what is the equilibrium concentration of $\text{Cl}^-(aq)$ ? | | $\text{Cu}^+$ | $\text{Cl}^-$ | | - | ------------- | ------------- | | I | 0 | 0 | | C | + $s$ | + $s$ | | E | $s$ | $s$ | ICE table (in M):
A cell is constructed under standard conditions using Al(s)|Al $^{3+}$ (aq) and Pb(s)|Pb $^{2+}$ (aq) half-cells. Standard reduction potentials: Al $^{3+}$ + 3e $^-$ 6 Al(s), $E^\circ = -1.66\,\text{V}$ ; Pb $^{2+}$ + 2e $^-$ 6 Pb(s), $E^\circ = -0.13\,\text{V}$ . If Pb $^{2+}$ is reduced at the cathode, which statement is correct?
A student titrates a weak acid $\mathrm{HA(aq)}$ with a strong base $\mathrm{NaOH(aq)}$ and observes the typical curve: a gradual rise in pH, a buffering region, then a steep increase near the equivalence region, followed by a flatter post-equivalence region. If the student adds a small additional volume of $\mathrm{NaOH}$ while the titration is in the post-equivalence region, what happens to the pH?
A bond between atoms X and Y is polar, with Y being the more electronegative atom. Which of the following best represents the bond dipole?
For the reaction $\text{CaCO}_3(s)\rightleftharpoons \text{CaO}(s)+\text{CO}_2(g)$ at a certain temperature, $K$ is very small. What does this magnitude of $K$ imply about which side is favored at equilibrium?
For the reaction $\text{Fe}_2\text{O}_3(s)+2\text{Al}(s)\rightarrow 2\text{Fe}(s)+\text{Al}_2\text{O}_3(s)$ , $\Delta H=-851\ \text{kJ}$ . Which statement is correct?
A system consists of a mixture of ice and liquid water at 0°C and 1 atm. If a small amount of heat is added to the system, what is the immediate effect?
Consider the reversible reaction: $A_2(g) + B_2(g) \rightleftharpoons 2 AB(g)$ . A particulate representation of a sealed container at equilibrium shows 10 particles of AB, 2 particles of $A_2$ , and 2 particles of $B_2$ . Which statement correctly describes the equilibrium constant, $K_c$ , for this reaction?
A student compares the solubility of solid sodium benzoate, $\text{NaC}_6\text{H}_5\text{COO}(s)$ , in two solutions at the same temperature: (1) pure water and (2) pH 2 solution made with strong acid. Assume the solid dissolves to form $\text{Na}^+$ and $\text{C}_6\text{H}_5\text{COO}^-$ . Which best describes how pH affects the solubility and why?
Consider the following acids: I: HF II: HCl III: HBr IV: HI Which statement best explains the trend in acid strength down the group?
Two identical beakers are at 25°C. Beaker 1 contains 100 mL of pure water. Beaker 2 contains 100 mL of 1.0 M sucrose solution. The contents of the two beakers are poured together and stirred to form 200 mL of a more dilute, uniform sucrose solution. From initial state (two separate liquids) to final state (one mixed solution), how does the entropy of the system change?
A student measures the compressibility factor $Z=\dfrac{PV}{nRT}$ for a real gas in a container at low temperature and moderately high pressure and finds $Z<1$ . Relative to ideal-gas behavior, what deviation and cause are most consistent with this result?
The arrangement and movement of particles in liquid water are significantly influenced by strong hydrogen bonds, while the particles in liquid methane ( $\text{CH}_4$ ) are influenced only by weak London dispersion forces. This difference implies that, at the particulate level, liquid water exhibits...
A proposed mechanism for the overall reaction $\mathrm{2H_2O_2(aq) \rightarrow 2H_2O(l) + O_2(g)}$ is: Step 1 (slow): $\mathrm{H_2O_2 \rightarrow H_2O + O}$ Step 2 (fast): $\mathrm{O + H_2O_2 \rightarrow H_2O + O_2}$ Based only on the rate-determining step, which rate law is implied by the mechanism?
At a certain temperature, the equilibrium constant for $\mathrm{CaCO_3(s) \rightleftharpoons CaO(s) + CO_2(g)}$ is $K$ . What is $K_{\text{new}}$ for the reaction $\mathrm{CaO(s) + CO_2(g) \rightleftharpoons CaCO_3(s)}$ ?
At 25°C, 5.0 g of NaCl(s) is added to 100 mL of water in an open beaker and dissolves completely to form an aqueous solution. Considering the dissolving and mixing process for the system (salt + water), does entropy increase, decrease, or remain approximately constant?
A sealed syringe contains only liquid water at room temperature. The plunger is pulled back, and after a few seconds a mixture of liquid water and water vapor is observed inside the syringe. No other substances are present. Which statement best classifies this change?
Two acids are compared: I: formic acid, HCOOH II: acetic acid, CH3COOH Which best explains why formic acid is more acidic than acetic acid?
A proposed mechanism for the reaction $2\text{NO}(g)+\text{Br}_2(g)\rightarrow 2\text{NOBr}(g)$ is: Step 1 (slow, rate-determining): $\text{NO}(g)+\text{Br}_2(g)\rightarrow \text{NOBr}_2(g)$ Step 2 (fast): $\text{NO}(g)+\text{NOBr}_2(g)\rightarrow 2\text{NOBr}(g)$ Based only on the rate-determining step, which rate law is implied?
Sulfur dioxide, $\text{SO}_2$ , has a total of 18 valence electrons. If you draw a Lewis structure that keeps sulfur to an octet (no expanded octet), what must the bonding between S and O be?

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