# Thermodynamics multiple-choice - Horace Mann Webmail

Mechanics

Oct 27, 2013 (4 years and 8 months ago)

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Horace Mann School

AP Chemistry

Mr. Hatch

2006
-
07

Thermodynamics
Multiple
-
Choice Practice Questions

1.

CH
4
(g)

+ 2 O
2
(g)

= CO
2
(g)

+ 2 H
2
O
(l)

∆H˚ =

889.1 kJ

∆H
f
˚ H
2
O
(l)

=

285.8 kJ/mol

∆H
f
˚ CO
2
(g)

=

393.3 kJ/mol

What is the standard heat of formation
of methane, ∆H
f
˚ CH
4
(g)
, as calculated from the
data above?

(A)

210.0 kJ/mole

(D) 75.8 kJ/mole

(B)

107.5 kJ/mole

(E) 210.0 kJ/mole

(C)

75.8 kJ/mole

2.

A cube of ice is added to some hot water in a rigid, insulated container, which is then
sealed. There

is no heat exchange with the surroundings. What has hap
pened to the total
energy and the total entropy when the system reaches equilibrium?

Energy

Entropy

(A)

Remains constant

Remains constant

(B)

Remains constant

Decreases

(C)

Remains constant

Increa
ses

(D)

Decreases

Increases

(E)

Increases

Decreases

3.

For the reaction A
(g)

= B
(g)

+ C
(g)
, the equilib
rium constant, K
p
, is 2

4

at 25˚C. A
mixture of the three gases at 25˚C is placed in a reaction flask and the initial pressures are
P
A
= 21 atmo
sphere, P
B

= 0.5 atmosphere, and P
C
= 1 atmo
sphere. At the in
stant of
mixing, which of the following is true for the reaction as
written?

(A) ∆G < 0

(C) ∆S = 0

(E) ∆G˚ < 0

(B) ∆G > 0

(D) ∆G˚ = 0

4. Which of the following is a graph that describes the pathway of reaction that is endothermic
and has high acti
vation energy? (See Graph)

(A)

(B)

(C)

(D)

(E)

5. Whi
ch of the following must be true for a reaction that proceeds spontaneously from initial
standard state condi
tions?

(A)

∆G˚ > 0 and K
eq

> 1

(B)

∆G˚ > 0 and K
eq

< 1

(C)

∆G˚ < 0 and K
eq

> 1

(D)

∆G˚ < 0 and K
eq

< 1

(E)

∆G˚ = 0 and K
eq

= 1

6. H
2
O
(s)

= H
2
O
(l
)

When ice melts at its normal melting point, 273.16 K and 1 atmosphere, which of the
following is true for the pro
cess shown above?

(A)

∆H < 0, ∆S > 0, ∆V > 0

(B)

∆H < 0, ∆S < 0, ∆V > 0

(C)

∆H > 0, ∆S < 0, ∆V < 0

(D)

∆H > 0, ∆S > 0, ∆V >0

(E)

∆H > 0, ∆S

> 0, ∆V < 0

1
-
C 2
-
C 3
-
B 4
-
A 5
-
C 6
-
E