314 ❯ STEP 5. Build Your Test-Taking Confidence- While the titration of a diprotic acid to produce a
curve similar to the idealized one above is useful
in many analyses, ascorbic acid is not a good can-
didate for this type of analysis. Why?
(A) Ka2 and Ka1 are too close together.
(B) Ascorbic acid may occur in more than one
form.
(C) Ascorbic acid is not soluble in water.
(D) Ka2 for ascorbic acid is too small. - Which of the following CANNOT behave as
both a Brønsted base and a Brønsted acid?
(A) H 2 PO 42 -
(B) CO 32 -
(C) HSO 3 -
(D) HCO 3 - - A student mixes 50.0 mL of 0.10 M potassium
chromate, K 2 CrO 4 , solution with 50.0 mL of
0.10 M AgNO 3. A red precipitate of silver chro-
mate forms and the concentration of the silver
ion becomes very small. Which of the following
correctly places the concentrations of the remain-
ing ions in order of decreasing concentration?
(A) [K+] > [CrO 42 - ] > [NO 3 - ]
(B) [CrO 42 - ] > [NO 3 - ] > [K+]
(C) [K+] > [NO 3 - ] > [CrO 42 - ]
(D) [NO 3 - ] > [K+] > [CrO 42 - ] - There are a number of experiments for the deter-
mination of the molecular mass of a gas. One
method begins by heating a solid or liquid in
a flask to produce a gaseous product. The gas
passes through a tube and displaces water in an
inverted, water-filled bottle. The mass of the start-
ing material is measured, along with the volume
of the displaced water and the temperature of the
system. The pressure in the inverted water-filled
bottle is equal to the external pressure. Once the
barometric pressure has been recorded, what other
information is needed to finish the experiment?
(A) The heat of formation of the gas
(B) The density of the water
(C) The mass of the displaced water
(D) The vapor pressure of the water
H 2 (g) + 1/2 O 2 (g) → H 2 O(l) ΔH° = - 300 kJ
C(s) + O 2 (g) → CO 2 (g) ΔH° = - 400 kJ
C 2 H 2 (g) + 5/2 O 2 (g) →
H 2 O(l) + 2 CO 2 (g) ΔH° = - 1300 kJ
21. Using the information given above, calculate the
enthalpy change for the following reaction:
2 C(s) + H 2 (g) → C 2 H 2 (g)
(A) 200 kJ
(B) -200 kJ
(C) 500 kJ
(D) -500 kJ
22. Cerium(III) sulfate, Ce 2 (SO 4 ) 2 , is less soluble in
hot water than it is in cold. Which of the follow-
ing conclusions may be related to this?
(A) The heat of solution of cerium(III) sulfate is
exothermic.
(B) The hydration energies of cerium ions and
sulfate ions are very low.
(C) The heat of solution for cerium(III) sulfate
is endothermic.
(D) The solution is not an ideal solution.
Use the information on the containers in the fol-
lowing diagram to answer questions 23–25.
A
He
250 K - 0 mole
- 0 L
B
CH 4
250 K- 0 mole
- 0 L
C
O 2
250 K- 0 mole
- 0 L
D
SO 2
250 K- 0 mole
- 0 L
Approximate molar masses:
He = 4 g mol-^1 , CH 4 = 16 g mol-^1 ,
O 2 = 32 g mol-^1 , SO 2 = 64 g mol-^1- Under the conditions indicated, in which of the
gas sample is the average velocity of the molecules
half that of methane, CH 4?
(A) He
(B) CH 4
(C) SO 2
(D) They are all at the same temperature; there-
fore, they have the same average velocity. - Which of the four gases will probably show the
least deviation from ideal behavior?
(A) He
(B) CH 4
(C) O 2
(D) SO 2
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20-Moore_PE01_p307-340.indd 314 31/05/18 1:58 pm