27 Colligative Properties

# 27 Colligative Properties - The atmosphere on a distant...

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1 1 The atmosphere on a distant planet is entirely carbon dioxide at a pressure of 1520 torr (2 Earth atmospheres). What would the pH of a lake on this planet be if both the hydronium ion and hydrogen carbonate concentrations were determined by the dissolved carbon dioxide? Henry’s law constant for CO 2 = 0.030 M/atm. pK 1 for carbonic acid (H 2 CO 3 ) = 6.37 [CO 2 ] = 1000 [H 2 CO 3 ] A) 5.3 B) 3.1 C) 3.5 D) 4.1 E) 8.5 2 x - 6.0x10 x 10 x x x - M 10 6.0 x x x - 0 0 atm) M/atm)(2 (0.030 1000 1 HCO O H 0 H CO H 5 - 2 6.37 - 5 - - 3 3 2 3 2 x If you neglect x in the denominator, you find x = 5.1 x 10 -6 and pH = 5.29. Note 6.0 x 10 -5 / 5.1 x 10 -6 = 11.8 If you do the quadratic equation thing, you find x = 5.3 x 10 -6 and pH = 5.28.

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2 3 What do you think? The vapor pressure of sea water is _____________ the vapor pressure of pure water? A) higher than B) the same as C) lower than 4 Fig. 15-14, p. 745 A really neat measurement of the difference!
5 Today’s To Do Make correct calculations of colligative properties of solutions: Vapor Pressure Lowering Boiling Point Elevation Freezing Point Depression Osmotic Pressure Colligative means depending on the number of particle and not on the nature of the particles. 6 Measurement shows that the vapor pressure of salty water is linearly proportional to the mole fraction of the water (solvent) in the solution. The vapor pressure of the solvent is lowered by the presence of non-volatile solute particles. A colligative property!

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## This note was uploaded on 03/29/2010 for the course CHE 132 taught by Professor Hanson during the Spring '08 term at SUNY Stony Brook.

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27 Colligative Properties - The atmosphere on a distant...

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