1. A solution contains 11.60g of unknown compound dissolved in 50.0 mL of water.

Question

1. A solution contains 11.60g of unknown compound dissolved in 50.0 mL of water. (Assume a density of 1.00 g/mL for water.) The freezing point of the solution is -4.79?C. The mass percent composition of the compound is 53.31% C, 11.19% H, and the rest is O. What is the molecular formula of the compound? Express answer as a molecular formula.

2. Calculate the vapor pressure of a solution containing 28.0g of glycerin (C3H8O3) in 134mL of water at 30.0 ?C. The vapor pressure of pure water at this temperature is 31.8 torr. Assume that glycerin is not volatile and dissolves molecularly (i.e., it is not ionic) and use a density of 1.00 g/mL for the water.

3. Calculate the osmotic pressure of a magnesium citrate laxative solution containing 29.0g of magnesium citrate in 221mL of solution at 37 ?C(approximate body temperature). Assume complete dissociation of the ionic compound.

4.Use Henry's law to determine the molar solubility of helium at a pressure of 1.2atm and 25 ?C. Henry

Explanation / Answer

(0.0170 g H2O) / (18.01532 g H2O/mol) = 0.00094364 mol H2O
P = nRT / V = (0.00094364 mol) x (62.36367 L?mmHg/K?mol) x (25 + 273)K / (1 L) = 17.54 mmHg H2O

You need to know the vapor pressure of pure water at 25

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