Chem
1115 – Unit 6 Practice Problems
1.
Convert
525 torr to
2.
Convert
32.0 psi to mm Hg.
3.
What
is the volume of 0.250 moles of a gas at 75oC and 1.50 atm?
4.
A
25.0 g sample of CO2 is placed in an 8.00 L steel tank. What is the pressure in torr in the tank at
45oC?
5.
How
many moles of a gas are present in 25.0 L steel tank at 1.5 x 102
kPa and 165oC?
6.
At
what temperature in oC would 25.0 g of NH3 in a 27 L
steel tank have a pressure of 1.5 atm?
7.
A
sample of gas in a 1.00 L cylinder-piston assembly has a pressure of 2.50 x 105
Pa at 115oC. If the gas is
cooled to room temperature (25oC) and the gas is compressed to a
volume of 550 mL, what is the pressure (in SI units) of the gas.
8.
A
sample of gas in a 35.0 L cylinder-piston assembly has a pressure of 1.40 atm
at 125oC. If the pressure on
the gas increases to 3.3 atm while the volume of the gas decreases to 25.0 L,
what is the temperature (oC) of the gas?
9.
What
is the molar mass of a gas if it has a density of 2.55 g/L at 22oC
and 1.25 atm?
10.
What
is the density of NH3 (g) at 35oC and 755 torr?
11.
Use
the following equation to answer the questions below:
2 C2H2 (g) + 5 O2 (g) à 4 CO2 (g) + 2 H2O (g)
a)
How
many moles of O2 are needed to react with 15.0 mL of C2H2
at 125oC and 1.25 atm?
b)
How
many liters of CO2 (g) are produced from 15.0 grams of C2H2
(g) at STP?
c)
How
many liters of CO2 (g) at 75oC and 725 torr are produced
from 27.0 L of C2H2 (g) at 175oC and 850 torr?
12.
What
is the partial pressure of He in a tank with a total pressure of 850 torr if it
contains 0.500g of
He, 1.505 g O2 , and 0.732 g N2?
13.
At
35oC water has a vapor pressure of 42.2 torr. What is the partial pressure of a gas if the
total pressure of the gas collected over water is 1.234 atm?
14.
Calculate
the change in internal energy that occurs when a system absorbs 175 kJ of heat
while performing 105 kJ of work on the surroundings.
15.
Calculate
the change in internal energy that occurs when the surrounding do 975 kJ of
work on the system while the system absorbs 116 kJ of heat.
16.
Use
dimensional analysis and the conversion factors given in your notes (or the
back of your book) to convert 130,000 BTU to kilojoules.
17.
The
specific heat of aluminum is 0.900 J/g.K. Use this information to answer the questions
below.
a. Calculate the amount of heat needed to raise the temperature of
125 grams of aluminum from 22.7oC to 85.6oC.
b. If 1.72 kJ of heat are added to 165 g of aluminum, calculate the
temperature change that would occur.
c. If the initial temperature for the aluminum described in part b is
19.7oC, what will its final temperature be?
18.
Calculate
the specific heat of gasoline if 4440 J of heat are
needed to raise the temperature of 100.0 g of gasoline from 19.3oC
to 39.3oC.
19.
The
heat of vaporization for water is 40.7 kJ/mole. Calculate the amount of heat needed to
convert 75.0 g of water at 100oC to steam at the same temperature.
20.
The
heat of fusion of water is 6.01 kJ/mole. Calculate the amount of heat needed to
convert 127.5 g of ice at 0oC to water at the same temperature.
21.
The
heat of fusion of water is 6.01 kJ/mole. Calculate the enthalpy change that occurs
when 127.5 g of water at 0oC is converted to ice at the same
temperature.
22.
The
heat of fusion of water is 6.01 kJ/mole while its heat
of vaporization is 40.7 kJ/mole. The
specific heat of steam, water, and ice are 1.84 J/gK, 4.18 J/gK, and 2.09 J/gK,
respectively. Calculate the amount of
heat needed to convert 250.0 g of ice at 0.oC to steam at 100.oC.
23.
Silver
has a melting point of 961oC and a boiling point of 2212oC. The specific heat of solid Ag is 0.238 J/g.K
while the specific heat of liquid Ag is 0.285 J/g.K. The heat of vaporization of silver is 254 kJ/mol while its heat of fusion is 1.30 kJ/mol. How much heat (in kJ) is gained or
lost when 125 grams of solid silver at 25oC are converted to the
liquid state at 961oC. (You
may or may not need all data given.)
24.
The
combustion of methylhydrazine (CH6N2) is described by the
following thermochemical equation. Use
this information to answer the questions below.
2 CH6N2
(l) + 5 O2 (g) à 2 N2 (g) + 2 CO2 (g)
+ 6 H2O (l) H =
-2.60 x 103 kJ
a. Is the reaction endothermic or exothermic?
b. Is heat gained or lost during combustion?
c. Calculate the enthalpy change that occurs during the combustion of
6.93 kg of methylhydrazine.
d. Calculate the enthalpy change that occurs when 7.44 moles of water
are formed by the combustion of methylhydrazine.
e. Calculate the mass of oxygen consumed during this reaction when an
enthalpy change of -4.32 x 104 kJ occurs.
f. What is the enthalpy change for the following reaction?
2 N2 (g) + 2 CO2
(g) + 6 H2O (l) à 2 CH6N2 (l) + 5 O2
(g)
25.
Identify
each of the following phase changes as endothermic or exothermic.
a. vaporization
b. melting
c. condensation
d. freezing
e. sublimation
26.
Use
the phase diagram below to answer the following questions.
a. What phase change occurs
going from point B to A?
b. What phase change occurs
going from pont G to H?
c. What physical state(s) is/are present
at point F?
d. What physical state(s) is/are present
at point D?
e. What physical state(s) is/are present
at point E?
f. Which point represents the triple point
of the substance?
27.
Write
the correct formula for the following compounds:
a. sodium bicarbonate
b. dinitrogen trioxide
c. tetraphosphorus decoxide
d. barium hydroxide
e. phosphoric acid
f. iron (III) carbonate
g. hydrochloric acid
h. ammonium sulfate
i. nitric acid
28.
Write
the balanced equation for the reaction between aqueous solutions of sodium
carbonate and aluminum nitrate.
29.
Calculate
the volume of 17.22 g of a substance that has a density of 2.44 g/cm3.
30.
Calculate
the molarity of a solution that contains 2.92 g of sodium hydroxide per 50.00
mL of solution.