Ch. 10.5, 8.9, 11.4, 19  gas & thermodynamics            test     [75 points]                               AP Chem

For problems involving calculations, show your work in an organized manner, include any relevant equation (or formula and conversion factor(s)), put the proper units in your calculations / answer, and have the proper number of significant figures in your answer.

Academic Honesty:   The answers on this test are my own and I am using only the allowed set of notes as described in the syllabus.  I have not discussed the test questions with anyone before or during the test nor have I seen the test questions prior to the exam.  If you violate any of the preceding items or do not sign, your semester grade is a F.

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1.  A syringe has a volume of 23.0 mL and is open to the atmosphere, where it’s pressure is 755 torr and the temperature is 21.0 °C. The syringe was sealed, then transferred to a refrigerator at 4.0 °C.  What is the pressure in the syringe in the refrigerator ?  [10 points]

2.  Based on thermodynamics, estimate the boiling point of butane.  [10 points]

3.  Heating a sample of potassium chlorate, KClO3, generates potassium chloride and oxygen gas.  The gas was collected over water (see below figure – it’s figure 10.13 in your textbook).  Based on the following hypothetical experimental data:  [20 points]

Volume of gas = 250.0 mL

Room temperature = 26.0 °C

Atmospheric pressure = 755 mm Hg

Height of water in the beaker = 25 cm water [assume: 10.3 meters of water = 1.0 atm]

[]

a.  what is the pressure of the gases in the inverted beaker ?

b.  what is the partial pressure of oxygen in the beaker ?

c.  what is the number of moles of oxygen in the beaker ?

d.  what is the number of grams of KClO3 that was heated ?

4.  Without any calculations, determine ΔS (i.e. positive, negative, ambiguous) of __;  justify / rationalize your answer.  [15 points]

a. Synthesis of ammonia from hydrogen and nitrogen

b.  Dissolving solid potassium chloride in water

c. Mixing aqueous solutions of silver nitrate and sodium chloride

5.  What is the maximum number of grams of ice (i.e. solid H2O) at 0 °C that could melt (to form liquid water at 0 °C) by the completion combustion of 1.0 grams of pentane ? [20 points]