5 Steps to a 5 AP Chemistry 2019

AP Chemistry Practice Exam 1 ❮ 317

38. A student prepares three buffer solutions. Each
    solution is 1.0 M in one of the acids in the table
    and 1.0 M in its corresponding sodium salt.
    Which of the solutions has the greatest buffer
    capacity with respect to added NaOH and why?
    (A) The benzoic acid buffer because it is the
    strongest acid.
    (B) The chloroacetic acid buffer because it is
    the strongest acid.
    (C) The formic acid buffer because it donates
    both of its hydrogen atoms.
    (D) All are the same.


39. Hypochlorous acid is an unstable compound,
    and one of the decomposition products is chlo-
    rine gas, Cl 2. The decomposition of the acid
    lowers its concentration over time. What effect
    will the decomposition of one-fourth of the acid
    have on the agreement between the endpoint of
    the titration and the equivalence point during a
    titration with standard sodium hydroxide?
    (A) The endpoint would still remain near the
    ideal equivalence point.
    (B) The endpoint would be after the ideal
    equivalence point.
    (C) The endpoint would be before the ideal
    equivalence point.
    (D) It is impossible to determine.


40. Three 25.00 mL samples of approximately
    0.10 M phenol, C 6 H 5 OH, Ka = 1.0 × 10 -^10 were
    removed from a container and placed in separate
    250 mL beakers. The samples were titrated with
    standard potassium hydroxide, KOH, solution.
    Cresol red was the acid-base indicator used in
    the titration. The samples required 31.75, 32.38,
    and 41.75 mL to reach the endpoint. Which
    of the following might explain why one of the
    samples required significantly more base to reach
    the endpoint?
    (A) The indicator was added too late.
    (B) The wrong indicator was used.
    (C) There was a base contaminating the unclean
    beaker.
    (D) There was an acid contaminating the
    unclean beaker.
    41. During the study of the reaction A → 2B, a
    chemist constructs several graphs. The graph of
    [A] versus time and the graph of ln [A] versus
    time both give a curved line; however, the graph
    of 1/[A] versus time and gives a straight line. This
    implies the rate law is
    (A) Rate = k[A]
    (B) Rate = k[A]^2
    (C) Rate = k[A]^0
    (D) Rate = k[A]-^1
    42. The photoelectron spectrum of carbon has three
    equally sized peaks. What peak is at the lowest
    energy?
    (A) The 1s peak has the lowest energy.
    (B) The 2s peak has the lowest energy.
    (C) The 2p peak has the lowest energy.
    (D) The 1p peak has the lowest energy.

COMPOUND FORMULA

MOLAR

MASS

(g mol-^1 )

BOILING

POINT

(çC)

Ethyl methyl

ether

C 2 H 5 -O-CH 3 60.10 10.8

Ethyl methyl

amine

C 2 H 5 NH-CH 3 59.11 36.7

Propylamine C 3 H 7 NH 2 59.11 47.8

Trimethyl

amine

N(CH 3 ) 3 59.11 2.9

43. According to the data in the table above, which
    of the compounds has the strongest intermolecu-
    lar forces?
    (A) Propylamine
    (B) Ethyl methyl ether
    (C) Trimethyl amine
    (D) Ethyl methyl amine

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20-Moore_PE01_p307-340.indd 317 31/05/18 1:58 pm