478 CHAPTER 12: Gases and the Kinetic–Molecular Theory
0 *41.A 503-mL flask contains 0.0243 mol of an ideal gas at a
given temperature and pressure. Another flask contains
0.0388 mol of the gas at the same temperature and pres-
sure. What is the volume of the second flask?
*042.A laboratory technician forgot what the color coding on
some commercial cylinders of gas meant, but remem-
bered that each of two specific tanks contained one of the
following gases: He, Ne, Ar, or Kr. Measurements at STP
made on samples of the gases from the two cylinders
showed the gas densities to be 3.74 g/L and 0.178 g/L.
(a) Determine by calculation which of these gases was
present in each tank. (b) Could this determination be
made if the densities had been at a temperature and pres-
sure different from STP?The Ideal Gas Equation
*043.Calculate Rin Latm/molK, in kPadm^3 /molK, in
J/molK, and in kJ/molK.
*044.(a) What is an ideal gas? (b) What is the ideal gas equa-
tion? (c) Outline the logic used to obtain the ideal gas
equation. (d) What is R? How is it obtained?
*045.(a) A chemist is preparing to carry out a reaction at high
pressure that requires 36.0 mol of hydrogen gas. The
chemist pumps the hydrogen into a 12.3-L rigid steel con-
tainer at 25°C. To what pressure (in atmospheres) must
the hydrogen be compressed? (b) What would be the den-
sity of the high-pressure hydrogen?
*046.Calculate the pressure needed to contain 2.44 mol of an
ideal gas at 45°C in a volume of 3.70 L.
*047.(a) How many molecules are in a 1.00-L container of
gaseous oxygen if the pressure is 2.50 10 ^9 torr and the
temperature is 1225 K? (b) How many grams of oxygen
are in the container?
0 *48.A barge containing 580. tons of liquid chlorine was
involved in an accident. (a) What volume would this
amount of chlorine occupy if it were all converted to a
gas at 750. torr and 18°C? (b) Assume that the chlorine
is confined to a width of 0.500 mile and an average depth
of 60. ft. What would be the length, in feet, of this chlo-
rine “cloud”?Molecular Weights and Formulas for Gaseous
Compounds
*049.Analysis of a volatile liquid shows that it contains 37.23%
carbon, 7.81% hydrogen, and 54.96% chlorine by mass.
At 150.°C and 1.00 atm, 500. mL of the vapor has a mass
of 0.922 g. (a) What is the molecular weight of the com-
pound? (b) What is its molecular formula?
0 *50.A student was given a container of ethane, C 2 H 6 , that had
been closed at STP. By making appropriate measure-
ments, the student found that the mass of the sample of
ethane was 0.244 g and the volume of the container was
185 mL. Use the student’s data to calculate the molecu-lar weight of ethane. What percent error is obtained?
Suggest some possible sources of the error.
*051.Calculate the molecular weight of a gaseous element if
0.480 g of the gas occupies 367 mL at 365 torr and 45°C.
Suggest the identity of the element.
*052.A cylinder was found in a storeroom of a manufacturing
plant. The label on the cylinder was gone and no one
remembered what the cylinder held. A 0.00500-gram
sample was found to occupy 4.13 mL at 23°C and 745
torr. The sample was also found to be composed of only
carbon and hydrogen. Identify the gas.
*053.A sample of porous rock was brought back from the planet
Farout on the other side of the galaxy. Trapped in the
rock was a carbon–oxygen gas. The unknown gas was
extracted and evaluated. A volume of 3.70 mL of the gas
was collected under the conditions of STP. The mass of
the gas sample was determined to be 0.00726 grams.
Additional analysis proved that there was only one com-
pound present in the sample. What was the most probable
identity of the gas based on these analyses?
0 *54.A highly volatile liquid was allowed to vaporize com-
pletely into a 250.-mL flask immersed in boiling water.
From the following data, calculate the molecular weight
(in amu per molecule) of the liquid. Mass of empty
flask65.347 g; mass of flask filled with water at room
temperature327.4 g; mass of flask and condensed
liquid65.739 g; atmospheric pressure743.3 torr;
temperature of boiling water99.8°C; density of water
at room temperature0.997 g/mL.
*055.A pure gas contains 85.63% carbon and 14.37% hydro-
gen by mass. Its density is 2.50 g/L at STP. What is its
molecular formula?Gas Mixtures and Dalton’s Law
*056.(a) What are partial pressures of gases? (b) State Dalton’s
Law. Express it symbolically.
*057.A sample of oxygen of mass 30.0 g is confined in a ves-
sel at 0°C and 1000. torr. Then 8.00 g of hydrogen is
pumped into the vessel at constant temperature. What
will be the final pressure in the vessel (assuming only mix-
ing with no reaction)?
*058.A gaseous mixture contains 5.23 g of chloroform, CHCl 3 ,
and 1.66 g of methane, CH 4. What pressure is exerted by
the mixture inside a 50.0-mL metal container at 275°C?
What pressure is contributed by the CHCl 3?
*059.A cyclopropane–oxygen mixture can be used as an anes-
thetic. If the partial pressures of cyclopropane and oxygen
are 140. torr and 560. torr, respectively, what is the ratio
of the number of moles of cyclopropane to the number
of moles of oxygen in this mixture? What is the corre-
sponding ratio of molecules?
*060.What is the mole fraction of each gas in a mixture hav-
ing the partial pressures of 0.267 atm of He, 0.317 atm
of Ar, and 0.277 atm of Xe?