Chemistry 110
Mid-Term 2
October 24, 2002
NAME:__________________
Dr. Nash
100 Points Possible
constants: R=0.08206 L atm/mol K = 8.314 J/mol K
1. Hydrogen peroxide gas, H2O2, reacts with dichlorine monoxide, Cl2O to form
Chlorine dioxide gas, ClO2, and water vapor, H2O.
(a) Write a balanced chemical equation for this reaction.
(b) Is this a redox reaction, if so what is oxidized and what is reduced.
(c) Suppose you had a 7.57 L container holding hydrogen peroxide gas at 850 mmHg
pressure and 26.85 C. What volume of dichlorine monoxide gas at 126.85 C and 550
mmHg pressure will be needed to completely react with the hydrogen peroxide gas?
(d) Now, suppose I take 10.0 g of Cl2O and introduce it into a 10.0 L vessel containing
H2O2 gas at 100 C and 1.25 atm pressure. What is the limiting reagent and what is in
excess?
(e) When the reaction from part (d) is complete, the temperature is 125 C (and the
container still has a volume of 10.0 L). Calculate each of the following
P(H2O2)=
P(Cl2O)=
P(ClO2)=
P(H2O)=
P(total)=
(f) If when the reaction is finished you find the actual pressure of water vapor to be 400
mmHg, what is the percent yield of the reaction
(g) Calculate the pressures of each of the other gasses assuming this lower (less than
100%) yeild
P(H2O2)=
P(Cl2O)=
P(ClO2)=
P(H2O)=
P(total)=
(h) Ok, lets go back to assuming 100% yield for the reaction. When the reaction from (e)
is complete, the 10.0 L container breaks and at the other end of the room and a detector
registers the presence of the first gas to reach it after 22.8 seconds. What is the first gas
to reach you?
(i) After how long does the detector register the arrival of each the other gasses present?
(j) Suppose I lowered the temperature of the room, would that change the order in which
the gasses were detected? Why or why not?
(k) Calculate the root mean squared speeds of each of the gasses present.
(l) What would happen to these root mean sqared speeds of these substances if I
quadruple the temperature?
2. Gasseous Sulfur trioxide, SO3, dissolves in water to form sulfuric acid, H2SO4- a
strong acid.
(a) Sodium bisulfate, NaHSO4 is a salt of sulfuric acid that itself forms a weak acid when
dissolved in water. Write a chemical equation or chemical equations that can explain this
set of observations
(b) Suppose that 11.2 L of SO3 gas at 273.15 C and 760 mmHg dissolves in 500 mL of
water. What is the concentration of the resulting sulfuric acid solution
(c) Suppose this sulfuric acid solution reacts with aluminium hydroxide (you figure out
the formula). Write a balanced chemical equation for this reaction. If it occurs, what
is/are the driving force(s) of the reaction? Is it a redox reaction and if so, what is
oxidized and what is reduced?
(d) What volume of the sulfuric acid solution from (b) would be required to completely
react with 19.5 g of aluminium hydroxide.
3. 9.40 g of a compound containing only C and H are burned in excess oxygen to form
27.51 g of CO2 and 16.89 g H2O.
(a) What is the empirical formula of this compound?
(b) the molecular weight is found to be about 30 amu, what is its molecular formula?
(c) Write a balanced chemical equation for the combustion reaction of your compound
(d) Is this a redox reaction, if so what is oxidized and what is reduced?
BONUS:
So, our fearless leader (sarcasm intended) has declared that Iraq poses a clear, present,
and imminent danger to the United States because, in part, records show that many
thousands of aluminium tubes have been shipped to that nation. These tubes might be
useful in enriching uranium, one of the 'fissionable' actinides useful in nuclear weapons.
Unlike plutonium, the other actinide metal used in weapons, uranium occurs naturally
and does not have to be produced in reactors which are big, messy, and easy to detect.
Enriching uranium involves increasing the ratio of its isotope with a mass number of 235,
U-235, to that of the more commmon U-238 above the ratio that occurs naturally. Only
U-235 has the fission properties requisite in nuclear weapons so increasing this ratio is
necessary for any nation wishing to use the naturally occuring element uranium to make a
bomb. The infamous aluminium tubes would be useful in constructing a gasseous
diffusion apparatus which would enable this enrichment to occur. It works like this,
naturally occuring uranium containing both isotopes of the element is combined with
fluorine gas to form UF6 which is easlily turned into a gas. Because of its smaller mass, a
molecule of UF6 including the lighter isotope will move faster than one including the
heavier isotope. This provides a basis to separate the isotopes of the element and enrich a
sample of uranium in U-235. One simply allows the UF6 gas to diffuse over a very long
distance and viola! there you go. Unfortunately, UF6 is a highly corrosive substance and
therefore you need a great deal of special, expensive, and easily found (by weapons
inspectors) equipment (i.e. long tubes made of aluminium) to do this work.
So here is the question:
You are assigned to find a better way to separate uranium isotopes by the gasseous
diffusion method that does not require so much special (and detectable) equipment. You
and your chemists manage to make UCl6 and UH6. Which of these is a better candidate
for use in the gasseous diffusion apparautus and why? Are either of them better to use
than UF6 (aside from the corrosivity problem) and are either of them worse. Explain.
(you don't get points just for guessing- you have to explain why)