Ch. 13 & 15 gas & solution      test                 [60 points]                               honors 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.  Clearly identify the problems done and do them in sequence and your answer must begin and end on the same page of paper; otherwise, you will lose points.  attach this sheet to the front of your exam.

 

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 open to the atmosphere, where it’s pressure is 755 torr and 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.  Heating a sample of potassium chlorate, KClO3, generates potassium chloride and oxygen gas.  The gas was collected over water (see below figure).  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]

 

   

 

[image source:  http://wps.prenhall.com/wps/media/objects/3311/3391331/blb1006.html]

 

 

 

 

 

a.  what is the pressure of the gas in the container ?

 

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

 

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

 

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

 

3.  Describe how to prepare the following solutions; show relevant calculations.  [10 points]

 

a.  325 mL 25 mM calcium chloride

 

b.  325 mL 25 mM calcium chloride using a 135 mM calcium chloride solution.

 

4.  The boiling point of chloroform, CHCl3, is 61.2 °C, its Kb = 3.63 °C /m and Kf = 4.68 °C / m.  A fatty acid contains 72.0% carbon, 12.0% hydrogen, and 16.0% oxygen.  A solution containing 1.5 grams of the fatty acid dissolved in 10.0 grams of chloroform has a boiling point of 63.92 °C.   [20 points]

 

a.  what is the molality of the fatty acid in solution ?

 

b.  what is the molar mass of the fatty acid ?

 

c.  what is the chemical formula of the fatty acid ?