Version 385 – CH 302 Quiz 1 2014 – laude – (51790) 1
This print-out should have 10 questions.
Multiple-choice questions may continue on
the next column or page – find all choices
before answering.
001 5.0 points
You’re running late for class (again) and still
need to eat lunch. You remember Dr. Laude
saying something about how adding salt to
water increases the boiling point, thus allow-
ing faster cooking. If you have 1 cup (8 fl. oz.
= 250 mL = 250 g) of H2O, how many grams
of CaCl2should you add in order to raise the
boiling point from 100◦C to 105◦C?
1. 60.2 g
2. 135.5 g
3. 90.3 g correct
4. 361.3 g
Explanation:
∆Tb=m·i·kb
5 = m·3·0.512
m= 3.255
mass =m·V·M W
mass = 3.155 ·0.25 ·110.98
mass = 90.3
Or, without a calculator...
mass ≈3.2·0.25 ·110
mass ≈88
Which only leaves one right answer.
002 5.0 points
Water from a local stream is added to one
side of the U-tube shown below. Pure water
is placed in the tube on the other side of the
semipermeable membrane. With the left side
open to barometric pressure of 1.0 atm and
1.15 atm applied to the right side, the two
liquids do not move.
1.00 atm
1.15 atm
BA
In which half of the U-tube is the pure water
located?
1. Acorrect
2. B
3. Not enough information is given.
Explanation:
003 5.0 points
Both ammonia and phosphine (PH3) are sol-
uble in water. Which is least soluble and
why?
1. ammonia; the N−H bonds are so strong
that they cannot break to enable the ammonia
to hydrogen-bond with water.
2. phosphine; the P−H bonds are so strong
that they cannot break to enable phosphine
to hydrogen-bond with water.
3. ammonia; it is too small to be hydrated
by water molecules.
4. phosphine; it does not form hydrogen
bonds with water molecules. correct
5. ammonia; it does not form hydrogen
bonds with water molecules.
Explanation:
PH3is least soluble because it cannot form
hydrogen bonds with water.
004 5.0 points
Estimate the enthalpy of vaporization of CCl4
given that at 25◦C and 58◦C its vapor pressure
is 107 and 405 torr, respectively. Assume that
