1) Qualitative analysis revealed that an unknown contained the anions, NO3¯, Cl¯, and
ClO3¯. A student weighed a sample into a beaker and recorded the following data:
Weight of beaker and sample 68.962 grams
Weight of beaker
67.625 grams
The sample was dissolved and diluted to 200.0 milliliters. A 50.00-milliliter portion of
the solution was treated with excess silver nitrate solution, and the precipitate was
collected in a filter crucible. Weighings gave the following data:
Weight of crucible and AgCl 10.211 grams
Weight of crucible
10.102 grams
Another 50.00-milliliter portion was treated with a reducing agent before the addition of
excess silver nitrate solution. The precipitate which formed was collected and weighed in
another filter crucible.
Weight of crucible and AgCl 10.247 grams
Weight of crucible
10.110 grams
a) Determine the percentage of Cl¯ in the unknown.
b) Determine the percentage of ClO3¯ in the unknown.
2) The compound UF6 reacts with water to form a solid compound and a gas. It is found
that 1.76 grams of UF6 gives 1.08 liters of the gas at -13 °C and 0.400 atmosphere. The
gas is 95 per cent by weight flourine and 5 per cent by weight hydrogen, and its
molecular formula is assumed to be the same as its empirical formula.
a) What number of moles of gas is formed?
b) What number of gram-atomic weights of flourine is removed from one mole of UF6?
c) What is the empirical formula of the solid compound?
3) A 100.0-milliliter sample of a solution of sodium hydroxide contaminated with
carbonate was standardized using methyl orange (pK = 4) as the indicator. The titration
required 27.50 milliliters of 0.2000-molar H2SO4. A second 100.0-milliliter sample of the
base was titrated with the same acid using phenolphthalein (pK = 8) as an indicator. This
titration required 26.50 milliliters of acid.
a) What is the molarity of the NaOH in the solution?
b) What is the molarity of the CO32¯ in the solution?
14) Give the definition of a base according to EITHER the Bronsted-Lowry OR the
Lewis concept. Which of the following substances are bases according to the definition
you have given?
O2¯, HSO4¯, Ar, HF, H¯, Cu(NH3)42+
For one of the above substances which you have classified as a base, write an equation
illustrating its basic character according to the definition you have given.
15) Describe the effect of changes in temperature and pressure on the rate of a chemical
reaction involving gases. Explain why each factor affects the rate as it does.
16) As a solution of sodium chloride is added to an equilibrium mixture of solid silver
chloride and water, the weight of solid present first increases and then decreases. Explain.
17) The ionization energies of lithium and sodium are 5.39 and 5.14 electron volts
respectively. The standard half-cell (oxidation) potentials are as follows:
Li ---> Li+ + e ¯ E ° = 3.02 volts
Na ---> Na+ + e¯ E ° = 2.71 volts
Explain the apparent contradiction of these two sets of data as to the relative ease of
removing an electron from atoms of these elements.
18) Describe two ways by which the presence of cadmium ion Cd2+, could be detected in
the presence of a fairly high concentration of copper (II) ion, Cu2+. Illustrate with
equations.
19) Describe three types of particles emitted in nuclear transformations and indicate the
changes in the nuclei with result from the emission of each of these types of particles.
20) Point out significant differences in the physical properties of the four substances,
neon, ammonia, silicon dioxide, and potassium chloride. Account for these differences in
terms of chemical bonding theory.
21) Many of the properties of solutions depend on the concentration of the solute rather
than on the chemical nature of the solute. Discuss these colligative properties for ideal
and real solutions of strong electrolytes, weak electrolytes, and nonelectrolytes.