5 Steps to a 5 AP Chemistry 2019

AP Chemistry Practice Exam 1 ❮ 321

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1 L

300 K 300 K 200 K 300 K

++ 2 L41 L L

53. The contents in the three containers on the left in
    the diagram above are transferred to the container
    on the right. The volumes of the original contain-
    ers are exactly the values indicated. The pressure
    in the first three containers is 1.0 atm. What is the
    pressure in the container on the right?
    (A) 3.0 atm
    (B) 4.0 atm
    (C) 1.1 atm
    (D) 0.50 atm

   

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OCOOCS

54. The diagram above shows the structure of mol-
    ecules of CS 2 and COS. The boiling point of
    COS is 223 K, and the boiling point of CS 2 is
    319 K. Which of the following is the best expla-
    nation of why the boiling point of CS 2 is higher?
    (A) The molar mass of CS 2 is greater.
    (B) COS has weaker covalent bonds than CS 2.
    (C) Only CS 2 can form intermolecular dipole-
    dipole forces.
    (D) COS has stronger intermolecular forces
    because it is polar and CS 2 is not.

Movable piston

CO(g) + Cl 2 (g)^ COCl 2 (g) ΔH = - 109 kJ

55. The above equilibrium is established in a closed
    system with a movable piston. After establish-
    ing equilibrium, the piston is rapidly moved
    up (pressure change). Which of the following
    graphs best illustrates the rate of the reverse reac-
    tion as the system returns to equilibrium?

(A)

Time

T jump

Reaction rate

(B)

Time

T jump

Reaction rate

(C)

Time

T jump

Reaction rate

(D)

Time

T jump

Reaction rate

2 I-(aq) + H 2 O 2 (aq) + 2 H+(aq) →

I 2 (aq) + 2 H 2 O(l)

The proposed mechanism for the above reaction is

as follows:

Step 1: H 2 O 2 (aq) + I-(aq) →

HOI(aq) + OH-(aq) (slow) k 1

Step 2: HOI(aq) + I-(aq) →

I 2 (aq) + OH-(aq) (fast) k 2

Step 3: 2 OH-(aq) + 2 H+(aq) →

2 H 2 O(l) (fast) k 3

20-Moore_PE01_p307-340.indd 321 31/05/18 1:58 pm