Chemistry 1212 Exam I Page 1 Name
Chemistry 1212
Exam I
Fall, 2000
Name______
All notes, books, etc., must be placed out of sight. Please read each of the problems carefully. If something is not clear, please ask.
The exam consists of 6 problems on 3 pages with extra credit opportunities on the third page. Make sure your exam is complete. The exam is worth 100 points with each of the problems labeled as to its point value.
Answers should be placed in the space provided and written legibly. If I cannot read it -- it is wrong. You MUST show your work clearly for each problem in order to receive full credit. Please include an explanation whenever asked to or whenever necessary to make your answer clear. If I cannot understand it -- it is wrong. Please put your name on every page of the exam.
There are scratch papers and periodic tables available for your use. If you require more data, please ask.
As usual, no cheating is allowed. Good Luck!
DATA
760 mm Hg = 760 Torr = 1 Atm
1 picture = 1 kiloword
Substance / Density / Freezing Pt / kfp / Boiling Pt / kbp / HvapH2O / 1.0 g/ml / 0.0 C / 1.86 / 100.0 C / 0.512 / 40.79 kJ/mole
Benzene / 0.8787 g/ml / 5.51 C / 5.12 / 80.2 C / 2.53 / 30.8 kJ/mole
1.(25) Consider the phase diagram shown here.
a)(3@) Give me estimated values for each of the following:
P T
Normal mp ______
Normal bp ______
Critical Point ______
Triple Point ______
b)(2@) Label each area with the correct physical state.
c)(4) What phase(s) is(are) present at point T?
d)(3) How does the density of the solid compare to the density of the liquid?
2.(20) The vapor pressure of methanol, CH3OH (MW = 32) is 94 torr at 20 ºC. The vapor pressure of ethanol, C2H5OH (MW = 46) is 44 torr at the same temperature. Consider a solution made from 50 grams of methanol and 50 grams of ethanol. Calculate the mole fraction of methanol and ethanol in the vapor observed above the solutions. Assume ideal behavior of the solution. Show all work clearly for full credit.
3.(5) Acetone is a widely used organic chemical whose structure is shown below. Acetone cannot participate in hydrogen bonding with itself as it lacks a hydrogen attached to a highly electronegative atom. However, it actively participates in hydrogen bonding with water, explaining its solubility in water. Show how this intermolecular bonding occurs with a simple, yet correct diagram.
4.(15) Sucrose (MW = 342) is dissolved in water to make a solution. Consider 100 grams of a 25% sucrose solution. You have both solid sucrose and distilled water available. How much of which one should you add to your 100 gram solution to produce a solution that is 2.5 m? Show all work clearly for full credit.
5.(15) The vapor pressure of benzene is 100.0 mm Hg at 26.1 ºC and 400.0 mm Hg at 60.6 ºC. What is the normal boiling point of benzene? Show all work clearly for full credit.
6.(20) A 1.60 g sample of a mixture of naphthalene (C10H8; MW = 128) and anthracene (C14H10; MW = 178) is dissolved in 20.0 grams of benzene (C6H6; MW = 78). The freezing point of the solution is 2.81 ºC. What is the composition of the sample mixture as a mass percent? Show all work clearly for full credit.