482 CHAPTER 12: Gases and the Kinetic–Molecular Theory
16.0°C. The vapor pressure of pure acetic acid at 16.0°C
is 400. torr. What should be the total mass of the col-
lected sample?
*111.The ideal gas equation deals with one set of volume, tem-
perature, and pressure conditions; the combined gas law
equation deals with two sets of conditions. Derive the
combined gas law equation from the ideal gas equation.
*112.Redraw Figure 12-12 so that it not only depicts the
decrease in space between molecules as the system is
cooled from 600. K to 300. K but also emphasizes the
change in kinetic energy.
*113.Suppose you were asked to supply a particular mass of a
specified gas in a container of fixed volume at a specified
pressure and temperature. Is it likely that you could ful-
fill the request? Explain.
*114.The gas molecules in the box undergo a reaction at con-
stant temperature and pressure.example earlier in this textbook where percent was used
instead of a fraction. Write an equation that relates mole
fraction and mole percent.
*117.Explain why gases at high pressure or low temperature
do not act as ideal gases.BUILDING YOUR KNOWLEDGE*118.A 5.00-L reaction vessel contains hydrogen at a partial
pressure of 0.588 atm and oxygen gas at a partial pres-
sure of 0.302 atm. Which element is the limiting reactant
in the following reaction?2H 2 (g)O 2 (g)88n2H 2 O(g)*119.Suppose the gas mixture in Exercise 118 is ignited and
the reaction produces the theoretical yield of the prod-
uct. What would be the partial pressure of each substance
present in the final mixture?
*120.A 0.422-g sample of pentane, C 5 H 12 , is placed in a
4.00-L reaction vessel with excess O 2. The mixture is then
ignited and the sample burns with complete combustion.
What will be the partial pressures of CO 2 and of H 2 O(g)
in the reaction vessel if the final temperature is 300.°C?
*121.When magnesium carbonate, MgCO 3 , is heated to a high
temperature, it decomposes.heat
MgCO 3 (s)888n MgO(s)CO 2 (g)A 20.29-gram sample of impure magnesium carbonate is
completely decomposed at 1000.°C in a previously evac-
uated 2.00-L reaction vessel. After the reaction was
complete, the solid residue (consisting only of MgO and
the original impurities) had a mass of 15.90 grams.
Assume that no other constituent of the sample produced
a gas and that the volume of any solid was negligible com-
pared with the gas volume. (a) How many grams of CO 2
were produced? (b) What was the pressure of the CO 2
produced? (c) What percent of the original sample was
magnesium carbonate?
*122.One natural source of atmospheric carbon dioxide is pre-
cipitation reactions such as the precipitation of silicates
in the oceans.Mg^2 (aq)SiO 2 (dispersed)2HCO 3 (aq)88n
MgSiO 3 (s)2CO 2 (g)H 2 O()How many grams of magnesium silicate would be pre-
cipitated during the formation of 100. L of carbon dioxide
at 30.°C and 775 torr?
*123.Table 12-2 states that dry air is 20.94% (by volume) oxy-
gen. What is the partial pressure of oxygen under the
conditions of STP? Hint:For gaseous samples the mole
ratios are equal to the volume ratios.If the initial volume is 1.8 L and the final volume is 0.9
L, which of the following boxes could be the products of
the reaction? Explain your reasoning.(a) (b) (c)(d) (e)*115.Use Dalton’s Law of Partial Pressures to illustrate the
changes that take place in the partial pressure of com-
pound A and the total pressure as gas B is pumped into
a closed system containing A.
*116.Mole fraction is one of the few quantities that is expressed
as a fraction. Frequently, percent is used instead. Cite an