Practice Test 1 - AP Chemistry

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

For the reversible reaction $\mathrm{A(g) + B(g) \rightleftharpoons C(g)}$ at a certain temperature, $K_c = 2.0$ . A reaction mixture is prepared with initial concentrations $[\mathrm{A}]=1.0\,\mathrm{M}$ , $[\mathrm{B}]=1.0\,\mathrm{M}$ , and $[\mathrm{C}]=0.50\,\mathrm{M}$ , and the system is not at equilibrium. Based on comparing $Q_c$ to $K_c$ , in which direction will the reaction proceed to reach equilibrium?
For the weak acid HF in water, $K_a=1.0\times10^{-4}$ at $25^\circ\text{C}$ . Which relationship between $K_a$ and $pK_a$ for HF is correct?
A student is comparing electromagnetic radiation used in different spectroscopic methods. Which ordering lists the regions from lowest photon energy to highest photon energy?
A liquid mixture contains $30.0\ \text{g}$ of acetone and $70.0\ \text{g}$ of water. What is the mass percent of acetone in the mixture?
A student has a mixture of cooking oil and water in a beaker. The liquids form two layers after standing. The student wants to separate the two liquids with minimal cross-contamination. Which method is best?
A solution is measured in a 1.00 cm cuvette and has $A=0.48$ . The molar absorptivity is $\varepsilon=1.6\times10^4\ \text{L mol}^{-1}\text{cm}^{-1}$ . What is the concentration?
A student compares two trials of the same reaction between a metal oxide solid and an acid solution. The mechanism is unchanged; only collision-related factors differ. Condition 1: The solid metal oxide is present as large pellets in the acid. Condition 2: The same mass of the solid metal oxide is ground into a fine powder before being added to the acid. Acid concentration, temperature, and stirring are the same. Which statement best explains why the reaction is faster in Condition 2 than in Condition 1, focusing on collision frequency at the solid surface?
Two lasers emit photons of different frequencies. Laser X emits light at $5.0\times10^{14}\ \text{s}^{-1}$ , and Laser Y emits light at $7.5\times10^{14}\ \text{s}^{-1}$ . Which statement is correct?
Solid silver acetate, $\text{AgC}_2\text{H}_3\text{O}_2(s)$ , is added separately to two solutions at the same temperature: Solution 1 is pure water and Solution 2 is adjusted to pH 2 with strong acid. Compared with Solution 1, the solubility in Solution 2 will be
The reaction of nitrogen and hydrogen to form ammonia is represented by the balanced equation $\mathrm{N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)}$ . If $0.60\ \text{mol}$ of $\mathrm{H_2}$ reacts with excess $\mathrm{N_2}$ , how many moles of $\mathrm{NH_3}$ are produced?
A student has an aqueous solution containing two dissolved dyes, one blue and one yellow. The dyes have different polarities, and the student wants to determine whether the sample contains one dye or a mixture. Which technique best accomplishes this separation and identification task?
In a metabolic pathway, two reactions are coupled by sharing intermediate $\mathrm{I}$ and occurring together. Reaction 1 is spontaneous: $\mathrm{S \rightarrow I}$ with $\Delta G = -12\ \mathrm{kJ\,mol^{-1}}$ . Reaction 2 is nonspontaneous: $\mathrm{I \rightarrow T}$ with $\Delta G = +12\ \mathrm{kJ\,mol^{-1}}$ . Based on thermodynamics, which statement best describes the overall coupled process?
A student adds a small amount of sodium chloride, NaCl(s), to distilled water and stirs until the solid is no longer visible. The resulting solution conducts electricity. Which statement best classifies the change that occurred to the NaCl?
Based on this information, what is the order of the reaction with respect to reactant A?
Element N is a noble gas in Group 18. Based on valence electrons and stability, which statement best describes the tendency of N to form a monatomic ion under typical conditions?
A student proposes the following mechanism for the net reaction $\mathrm{2SO_2(g) + O_2(g) \rightarrow 2SO_3(g)}$ : Step 1: $\mathrm{SO_2(g) + O_2(g) \rightarrow SO_4(g)}$ Step 2: $\mathrm{SO_4(g) + SO_2(g) \rightarrow 2SO_3(g)}$ Which statement about the mechanism is correct?
A student adds 1.0 g of iodine (I2), a nonpolar molecular substance, to 50 mL of hexane (C6H14), a nonpolar solvent, and stirs. Which statement best describes the result?
Use the standard enthalpies of formation, $\Delta H_f^\circ$ , given to calculate $\Delta H_{rxn}^\circ$ for the reaction below. $\text{CaCO}_3(s) \rightarrow \text{CaO}(s) + \text{CO}_2(g)$ Given: $\Delta H_f^\circ[\text{CaCO}_3(s)] = -1207\ \text{kJ/mol}$ , $\Delta H_f^\circ[\text{CaO}(s)] = -635\ \text{kJ/mol}$ , $\Delta H_f^\circ[\text{CO}_2(g)] = -394\ \text{kJ/mol}$ .
In the carbonate ion, $\mathrm{CO_3^{2-}}$ , carbon is the central atom with three C–O bonding regions (each bond, whether single or double in any resonance form, counts as one electron domain) and no lone pairs on carbon. What is the molecular geometry around carbon?
A sample of liquid water at $25^\circ\text{C}$ is converted to water vapor at the same temperature in an open container. Which statement correctly describes the enthalpy change for this phase change?

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