This is a two part solution. Part 1: KCl is an ionic salt with a formula weight

Question

This is a two part solution.

Part 1: KCl is an ionic salt with a formula weight of 74.54 g/mole. A 1.417 M (mole/liter) KCl solution has a density of 1064.5 grams/liter at 20 OC. Use the Molarity and the formula weight to find the mass (g) of salt in one liter. Then, find the mass (g and kg) of water in one liter of the solution. Determine the molality (m), or moles of salt per kg of water, by dividing the moles of salt in one liter by the kg of water in one liter. Show all units and use proper significant figures.

Part 2:

Suppose the KCl solution in part 1 is in contact with a semi-permeable osmosis membrane. Find the osmotic pressure using = iMRT. Show all units.

Explanation / Answer

PArt 1 :

Molarity of KCl solution = 1.417 = Moles of KCl / Litre of solution

Formula weight = 74.54

Moles = Mass of KCl / Formula weight

so mass of Kcl / Litres of solution = Molarity X formula weight = 1.417 X 74.54 = 105.62 grams

Molality = Moles / Kg of solvent

Mass of solution = Density of solution X volume of solution = 1064.5 X 1 Litre = 1064.5 grams = 1.0645 Kg

1.417 moles / Litres = 1.417 moles / 1.0645 Kg

so moles in 1Kg = 1.331

Molality = 1.331 moles / Kg

Part 2:

Osmotic pressure = i MRT

i = Vant Hoff factor = 2 (for KCl)

M = 1.417

R = 0.0821

T = 20 C = 293.15 K

Pressure = 2 X 1.417 X 0.0821 X 293 = 68.17 atm.

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