354 ❯ STEP 5. Build Your Test-Taking Confidence2 SO 2 (g) + O 2 (g) ^ 2 SO 3 (g)- The reaction above is allowed to continue until
equilibrium is established. After equilibrium is
established a catalyst is added to the system. How
does the rate of the forward reaction compare to
the rate of the reverse reaction after the addition
of the catalyst?
(A) The forward rate is faster than the reverse rate.
(B) The forward and reverse rates are the same.
(C) The reverse rate is faster than the forward rate.
(D) There is insufficient information to deter-
mine the relative rates.
A reaction has the following suggested mechanism: - NH 3 (aq) + OCl-(aq) → NH 2 Cl(aq) + OH-(aq)
- NH 3 (aq) + NH 2 Cl(aq) → Cl-(aq) + N 2 H 5 +(aq)
- OH-(aq) + N 2 H 5 +(aq) → N 2 H 4 (aq) + H 2 O(l)
- Referring to the above mechanism, which of the
following would support the suggested mechanism?
(A) Heating increases the rate of the reaction.
(B) Spectroscopy shows that N 2 H 5 +(aq) is pres-
ent in trace amounts.
(C) The rate constant does not change with
temperature.
(D) The first step is the rate-determining step. - Determine the final temperature, in °C, of a
sample of helium gas. The sample initially occu-
pied a volume of 5.00 L at 127°C and 875 mm Hg.
The sample was heated, at constant pressure,
until it occupied a volume of 10.00 L.
(A) 454°C
(B) 527°C
(C) 45°C
(D) 181°C
58. A solution contains 2.00 mole of acetic acid,
CH 3 COOH, and 1.00 mole of calcium acetate,
Ca(CH 3 COO) 2. The solution is able to resist the
addition of a small amount of strong acid or strong
base with only minor changes in the pH of the
solution. Larger quantities of strong acid or strong
base can cause a significant change in pH. How
many moles of nitric acid, HNO 3 , may be added
before the pH begins to change significantly?
(A) 0.500 mole
(B) 1.00 mole
(C) 2.00 mole
(D) 3.00 mole
Use the information in the following thermo-
chemical equations to answer questions 59–60.
C 2 H 5 OH(l) + 3 O 2 (g) →
2 CO 2 (g) + 3 H 2 O(l) ΔH = - 1370 kJ
2 H 2 (g) + O 2 (g) → 2 H 2 O(l) ΔH = - 570 kJ
2 H 2 (g) + O 2 (g) → 2 H 2 O(g) ΔH = - 480 kJ- Determine ΔH for the combustion of ethanol,
C 2 H 5 OH, if H 2 O(g) formed in the above reac-
tion instead of H 2 O(l).
(A) +1280 kJ
(B) -1280 kJ
(C) +1100 kJ
(D) -1100 kJ - What is the energy change when 72.0 g of water
vapor decomposes to the elements at constant
pressure? The molar mass of H 2 O is 18.0 g mol-^1.
(A) -1144 kJ
(B) -572 kJ
(C) +960 kJ
(D) +1144 kJ
STOP. End of AP Chemistry Practice Exam 2, Section I (Multiple Choice).21-Moore_PE02_p341-370.indd 354 31/05/18 1:54 pm