Final Exam Extra Credit
1-A sample of a saturated hydrocarbon is placed in a 1.0L vessel at 107oC. The pressure of the sample at
these conditions is .40 atm. A stoichiometrically equivalent amount of oxygen is added to the vessel and
the mixture is combusted. Following combustion, the pressure in the vessel is 5.19 atm at 107oC.
Assume all of the products are gases. What is the formula of the hydrocarbon? How many mols of
oxygen were added to the container?
2- Gases A2 and B2 react according to the equation: A2 + B2 → AxBy . If equimolar ( not necessarily
stoichiometrically equivalent) quantities are placed in a reaction vessel with a massless, frictionless
piston and allowed to react to completion. The density of the gas mixture after reaction is 1.5X the
original density. Find the empirical formula? Is there only one possibility? Explain.
3- An 8.68 gram sample of a mixture of aluminum carbonate and calcium carbonate is placed in a vessel
equipped with a massless, frictionless piston. The initial volume can be assumed to be zero. The sample
is heated to 800oC. This results in complete decomposition to the metal oxides and carbon dioxide. After
the reaction, the metal oxides are titrated to equivalence with 246.2 ml of 0.84 M HCl. If the
atmospheric pressure is 752 mm Hg, what is the maximum value for the volume of the reaction vessel?
4- Hydrogen and chlorine gas are placed in a 10.0 L container and allowed to react. The initial density of
the mixture is 5.01 x10-3 gm/ml. The vessel is at 300K and the initial pressure is 6.52 atm. After the
reaction is complete , the pressure is 6.52 atm. The gas is bubbled into 1.00 liter of deionized water. In
another part of the universe, a grey haired chemistry instructor prepares an acetic acid/ acetate buffer.
The buffer was prepared by adding acetic acid and sodium acetate to 2.50 L of deionized water. Now, as
universes collide, our hero adds 107 ml of the HCl solution to 405 ml of the buffer. The pH is measured
and is 4.35 after the HCl addition. A drop of phenolphthalein is added and the solution is titrated to
equivalence with 657 ml of 0.920 M NaOH. Calculate the original molarities of the weak acid and
conjugate base in the 2.50 L solution?