Chemistry 1212 Exam I Page 4 Name
Chemistry 1212
Exam I
Fall, 2007
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 7 problems on 4 pages with a Take-Home extra credit opportunity on the fourth 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
1 cm3 = 1 ml
1 meter = 100 cm
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
1.(15) What is the freezing point of an aqueous solution that boils at 106.5 °C? You must show all of your work clearly for full credit. Answers alone will receive little credit.
2.(20) Butane, C4H10 (MM = 58) has a heat of vaporization of 22.44 kj/mole and a normal boiling point of -0.4 °C. A 250 ml sealed flask contains 0.55 g of butane at -22 °C. When equilibrium is reached, how much butane will be present as a liquid? Show all work clearly for full credit.
Extra Credit: If the butane is warmed to 25 °C, how much is present as a liquid? If time allows, answer this on the back of the cover sheet. Show all work.
3.(15) An aqueous solution contains 12.5% NaCl (MM = 58.5) by mass. What mass of water (MM = 18) (in grams) is contained in 2.5 L of the vapor above this solution at 55 °C? The vapor pressure of pure water at 55 °C is 118 torr. Show all work clearly for full credit.
4.(10) Suppose 0.88 g of water (MM = 18) condenses on a 75.0 g block of iron (AM = 55.85) that is initially at 22 °C. If the heat released during condensation goes only to warming the iron block, what is the final temperature (in °C) of the iron block? Assume a constant enthalpy of vaporization for water of 44.0 kj/mole and the specific heat of iron is 0.449 j/g·°C.
5.(15)
The newly discovered element, braunium, found on the planet Koosban, has the following properties: MP = 10 °C; BP = 28 °C; TP = 8 °C, 0.8 atm; CP = 70 °C, 2.1 atm; vapor pressure of the solid at -10 °C is 0.3 atm.
a. Sketch the phase diagram for braunium
b. Label the axes
c. Label the phase areas (solid, liquid, vapor)
d. List a pressure value that you would expect braunium to sublime.
e. Would solid braunium sink or float in liquid braunium?
6.(20) An aqueous NaCl solution is made using 133 g of NaCl (MM = 58.5) diluted to a total solution volume of 1.00 L. If the density of this solution is 1.08 g/ml, calculate, showing all work clearly:
a. molarity
b. molality
c. mass percent
d. mole fraction NaCl
7.(5) A 0.100 M ionic salt solution has an osmotic pressure of 8.3 atm at 25 °C. Calculate the i (ionization) factor for this salt. Because of interactions that occur between solute particles, this may not be a whole number. Report your answer to two significant figures. Show your work.