총괄성. 증기압내림, Lowering the Vapor Pressure

총괄성. 증기압내림, Lowering the Vapor Pressure

 

 

A KCl solution is prepared by dissolving 40.0 g KCl in 250.0 g of water at 25℃.

What is the vapor pressure of the solution if the vapor pressure of water at 25℃ is 23.76 mmHg?

 

A) 20.5 mmHg    B) 22.1 mmHg    C) 22.9 mmHg    D) 25.5 mmHg

 

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ΔP = X_용질 × P°_용매    (∵ 비전해질 용질에서)

ΔP = i × X_용질 × P°_용매    (∵ 전해질 용질에서)

(i = van't Hoff factor)

 

 

용질의 mol수 = 40.0 g / (74.55 g/mol) = 0.537 mol

용매의 mol수 = 250.0 g / (18.02 g/mol) = 13.87 mol

전체 mol수 = 0.537 + 13.87 = 14.41 mol

X_용질 = 0.537 / 14.41 = 0.0373

 

 

ΔP = 2 × 0.0373 × 23.76 mmHg = 1.77 mmHg

23.76 – 1.77 = 21.99 mmHg

 

 

답: B)