1) A saturated solution of sulfur dioxide was prepared at 27 °C and 760 torr (millimeters of mercury). A 5.00-milliliter sample of this solution was diluted and an excess of potassium iodate solution was then added. The iodine liberated was equivalent to 32.80 milliliters of 0.100-molar sodium thiosulfate solution. The reactions that occur are given in the equations below:
5 SO2 + 2IO3¯ + 4 H2O --> 5 HSO4¯ + 3H+ + I2
2S2O32¯ + I2 --> 2I¯ + S4O62¯
(a) Calculate the moles of I2 liberated.
(b) Calculate the volume of sulfur dioxide at 27 °C and 760 torr needed to prepare 1.00 liter of the saturated sulfur dioxide solution.
2) The Kb at 25 °C of ammonia is 1.8 x 10¯5
(a) What is the pH of a buffer solution which is 0.10 molar in NH3 and 0.10 molar in (NH4)2SO4?
(b) What is the molar solubility of Sn(OH)2 in this buffer solution if the molar solubility of Sn(OH)2 in water is 7.4 x 10¯10 mole per liter and if the temperature is constant?
3) At 2,300 K and an initial water vapor pressure of 1.00 atmosphere, 1.00 per cent of the water is decomposed when equilibrium is established.
(a) What is the value for the equilibrium constant Kp for the decomposition of water at 2,300 K?
(b) A certain equilibrium mixture of H2, O2, and H2O at 2,300 K in a 2.00-liter container has 0.0004 mole of H2 and 0.0003 mole of O2. What is the molar concentration of H2O in this sample?
Questions 4 - 13 are not available.
14) The reaction of concentrated sulfuric acid with solid sodium fluoride or solid sodium chloride gives a good yield of hydrogen fluoride gas or hydrogen chloride gas. The reaction of concentrated sulfuric acid with solid sodium bromide or solid sodium iodide gives a poor yield of hydrogen bromide gas or hydrogen iodide gas. On the other hand, the use of concentrated phosphoric acid leads to hydrogen bromide and hydrogen iodide as well as hydrogen fluoride and hydrogen chloride. Interpret these observations on the reactions of concentrated sulfuric acid with the sodium halides.
15) Contrast the chemical behavior of SiCl4 and CCl4 when each is mixed with water. Explain the differences in terms of the electronic structures of SiCl4 and CCl4.
16) Name and discuss briefly the factor which is responsible for the spontaneity of an endothermic chemical reaction.
17) Name an ionic hydride and a covalent hydride. Give two pieces of evidence in support of each of your choices.
18) Explain why H3O+ is the strongest Bronsted acid that can exist in aqueous solution and why OH¯ is the strongest base. On the basis of your explanation, what species would be the strongest acid and what species would be the strongest base in liquid ammonia?
19) Tube I contains 10 grams of substance A at 60 °C, and tube II, also at 60 °C, contains 1 gram of substance B dissolved in 10 grams of A. As the tubes and their contents cool, temperature readings are taken at 1-minute intervals. For tube I the readings are as follows:
| 58.0°, | 56.0°, | 54.2°, | 52.8°, | 52.6°, | 52.6°, | 52.6°, | 52.5° |
For tube II the readings are:
| 58.0°, | 56.0°, | 54.0°, | 52.0°, | 50.2°, | 48.5°, | 48.0°, | 48.3°, | 48.6°, | 48.6°, | 48.6°, | 48.5°. |
The readings are also shown in the graphs below.
Discuss the significance of the data, identifying particular temperatures and their meanings.