1) An acidified solution of a sample of pure oxalic acid dihydrate, H2C2O4 . 2 H2O, was
used to standardize a solution of potassium permanganate. In this process, the oxalic acid
was oxidized to carbon dioxide and the permanganate ion was reduced to manganese(II)
ion. Use the following data to calculate the molarity (formality) of the permanganate
solution:
Weight of flask and acid crystals
68.6153 grams
Weight of flask
68.4262 grams
Burette reading after adding KMnO4 solution 31.52 mL
Burette reading before adding KMnO4 solution 1.51 mL
2) Two hydrocarbons, one a gas and the other a solid at room temperature, have the same
composition.
a) When either hydrocarbon is burned, the weight of carbon dioxide produced is 3.26
times the weight of water formed. Derive the empirical formula for the hydrocarbons
b) When 2.60 grams of the gas is placed in an evacuated 2.00-liter container, at 527 °C
the pressure is 1.20 x 103 millimeters of mercury. Determine the molecular weight of the
liquid hydrocarbon.
c) A solution of 3.25 grams of the solid hydrocarbon in 40.0 grams of benzene begins to
freeze at 2.969 °C. The freezing point of pure benzene is 5.533 °C and the molal freezing
point constant for benzene is 5.128 centigrade degrees. Determine the molecular weight
of the solid hydrocarbon.
3)
Zn(s) ---> Zn2+ + 2e¯ E°= 0.76 volt
Cu(s) ---> Cu2+ + 2e¯ E°= -0.34 volt
2.3 (RT/F) = 0.059 at 25 °C
A cell is set up to plate zinc onto a zinc electrode.
The loss of weight of a copper electrode is used to
determine the amount of current passed.
a) Assuming box A to be a source of direct current, if 100 milliliters of a solution of Zn2+,
initially at a 1.00-molar concentration, is electrolyzed until 1.00 per cent of the original
Zn2+ remains in solution,
1. how many coulombs are required?
2. how much weight does the copper electrode lose?
b) Assuming box A to be a voltmeter, what is the standard potential of the cell?
c) What is the minimum voltage to be applied to this cell if the electrolysis is to continue
until the concentration of Zn2+ reaches 1.00 per cent of the original? (Assume that the
concentration of Cu2+ reaches 1.00-molar and that the temperature is 25 °C.)
15) Criticize the statement. Chemical reaction tend to proceed in the direction of the
evolution of heat.
16) Explain why the spectra of gaseous atoms consist of sharp lines.
17) Give an explanation for each of the following observations:
a) The boiling point of CBr4 is distinctly higher than that of CCl4.
b) The boiling point of CH3OH is distinctly higher than that of CH3Cl.
18) In each of the following cases, a slight excess of dilute base is added to a 0.05-molar
solution of acid. The resultant heats of neutralization per mole of acid reacting are
indicated for each acid-base reaction.
Heat of Neutralization
a) HCl + NaOH
13.7 kcal.
b) HNO3 + KOH
13.7 kcal.
c) HCl + NH3
12.6 kcal.
d) CH3COOH + NaOH 13.4 kcal.
e) HClO4 + KOH
13.7 kcal.
19) Give an explanation for each of the following observations:
a) Many complex ions of zinc, such as Zn(CN)42-, exhibit a coordination number of four.
b) Complex ions of Fe(III), such as Fe(CN)63-, are paramagnetic.
20) The terms "activation energy" and "activated complex" (or "transition state") are
commonly employed in a theoretical discussions of rates of reaction. When is the
significance of these terms?
21) You are given a sample of ordinary sodium chloride, some glassware, a crucible, a 3volt battery, a ammeter, wires, distilled water, carbon tetrachloride, a bunsen burner, a
balance, equipment for supporting a crucible or beaker, and a selection of thermometers.
Your problem is to obtain experimental evidence for the assertion that sodium chloride is
electrovalently bonded. Describe a series of relevant observations and experiments.
Explain how the concept of ionic bonding gives a consistent interpretation of all of the
observations and experiments.
22) Discuss a chemical and a physical method for the determination of atomic weights.
State what experimental data are needed and show how the data may be employed to
achieve the desired objective. Indicate any assumptions that are made in the use of each
method.