QUESTION 1 1 points A KCI solution is prepared by dissolving 60.0 g KCl in 250.0

Question

QUESTION 1 1 points A KCI solution is prepared by dissolving 60.0 g KCl in 250.0 g of water at 25°C. What is the vapor pressure of the solution if the vapor pressure of water at 25°C is 23.76 mm Hg? 21.3 mm Hg 22.5 mm Hg 20.5 mm Hg 25.5 mm Hg QUESTION 2 1 points An aqueous solution has a normal boiling point of 105.0°C. What is the freezing point of this solution? For water Kb is 0.51°C/m and Kf 1.86°C/m -14.7°C 18.2°C 14.7°C 18.2°C 0 QUESTION 3 1 points The following diagram shows a close-up view of the vapor pressure curves for a pure solvent and a solution containing a nonvolatile solute dissolved in this solvent (a) (b Pressure (mm Hg) Temperature (°c) Which curve is the solvent and what happens to the vapor pressure when the solute is dissolved in the solvent? Curve (a) is the solvent and the vapor pressure decreases Curve (b) is the solvent and the vapor pressure increases Curve (a) is the solvent and the vapor pressure increases Curve (b) is the solvent and the vapor pressure decreases

Explanation / Answer

q.no:1

raoults law

P0-P/P0 = i*Xsolute

P0-P/P0 = n2 / n1+n2

i = vanthoffs factor of solute(KCl) = 2

P = vapor pressure of solution = ?

p0 = vapor pressure of pure water at this temperature = 23.76 mmhg

n1 = no of mol of solvent = (250/18) = 13.89 mol

n2 = no of mol of solute particles(KCl) = (60/74.55) = 0.805 mol

(23.76-x)/23.76 = 2*(0.805/(0.805+13.89))

P = vapor pressure of the solution = 21.16 mmhg

answer: 21.3 mmhg

q.no.2

DTb = i*kb*m

DTb = Tb-T0

i = vanthoff factor of solute = 1

T0 = boiling point of solvent(water) = 100 C

Tb = boiling point of solution = 105 C

kb for water = 0.51°C·kg/mol

m = molality of solution = ?

(105-100) = 1*0.51*x

x = 9.8

dTf = i*Kf*m

DTf = Tf-TS

Tf = freezingpoint of solvent = 0 c

Ts = freezingpoint of solution = ? c

i= vanthoff factor of solute = 1

Kf of water = 1.86 c/m

m = molality = 9.8 m

(0-x) = 1*1.86*9.8

x = Ts = - 18.2 C

answer: -18.2 C

q.no: 3

answer: Curve(a) is the solvent and the vapor pressure decreases

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