Exam 1 CH 302 Biberdorf - 282 version number signature...

signature:
282
version number
Shayak Sen (ss67795)
EXAM 1
Biberdorf Class (50203)
Water Data
K
f
= 1 . 86
◦
C/ m
K
b
= 0 . 512
◦
C/ m
C
ice
= 2 . 09 J/g
◦
C
C
water
= 4 . 184 J/g
◦
C
C
steam
= 2 . 09 J/g
◦
C
Δ H
fusion
= 334 J/g
Δ H
vapor
= 2260 J/g
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Version 282 – Exam 1 – biberdorf – (50203) 2
This print-out should have 20 questions.
Multiple-choice questions may continue on
the next column or page – find all choices
before answering.
001 4.0points
In which of the following will a given sam-
ple of PbBr
2
(
K
sp
= 4 . 6 × 10
− 6
)
be the least
soluble?
1. 100 mL of 0.01 M KOH
2. 100 mL of pure water
3. 100 mL of 0.002 M NaBr
4. 100 mL of 0.05 M HBr correct
5. 100 mL of 0.07 M HCl
Explanation:
PbBr
2
will have a common ion effect with
any solution with Pb
2+
or Br
−
in them. Two
of the solutions have Br
−
and those will cause
PbBr
2
to be less soluble. The 0.05 M HBr
solution has a higher concentration of Br
−
than the NaBr solution, which means it will
have the bigger effect on solubility, meaning
LESS PbBr
2
will dissolve in that solution.
002 4.0points
When 1.28 g of polypeptide are placed in
14.0 L of water at room temperature, the so-
lution exerts an osmotic pressure of 4.23 torr.
What is the molar mass of the polypeptide?
1. more than 550. g/mol
2. 38.8 g/mol
3. 158. g/mol
4. 402. g/mol correct
5. 388. g/mol
6. 40.1 g/mol
7. less than 25.0 g/mol
Explanation:
Π = iMRT polypeptide is non electrolyte
and i = 1
4.23/760 = (1) M (0.08206)(298.15)
M = 0 . 0002275 mol/L
x 14L = 0.003185 mol
1.28g/0.003186 mol = 402. g/mol
003 4.0points
A 9.386 M aqueous solution of sulfuric acid
has a density of 1.5091 g/mL. Calculate the
molality of sulfuric acid in this solution.
1. 6.81 m
2. 15.95 m correct
3. 12.84 m
4. 19.62 m
Explanation:
none
004 4.0points
A 250 gram sample of liquid water is heated
from 50
◦
C to vapor at 110
◦
C. What are
the signs for the change in enthalpy and the
change in entropy for this process?
1. Δ H > 0 , Δ S < 0
2. Δ H < 0 , Δ S < 0
3. Δ H = 0 , Δ S > 0
4. Δ H > 0 , Δ S > 0 correct
5. Δ H < 0 , Δ S > 0
Explanation:
None
005 4.0points
Which of the following shows the right equa-
tion for the ion product of iron(III) sulfate?