벤젠의 증기압은 26.1℃에서 100.0 torr

벤젠의 증기압은 26.1℃에서 100.0 torr

C6H6 vapor 26.1℃ 100.0 torr Raoult 26.1℃ 10.0% 100.0 mL 0.8765

C6H6 26.1℃ 100.0 torr 10.0% 100.0 mL density 0.8765

 

 

The vapor pressure of benzene, C6H6,

is 100.0 torr at 26.1℃.

Assuming Raoult’s law is obeyed,

how many moles of a nonvolatile solute

must be added to 100.0 mL of benzene

to decrease its vapor pressure by 10.0% at 26.1℃?

The density of benzene is 0.8765 g/cm3.

 

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100.0 torr × (90/100) = 90.00 torr

 

ΔP = 100.0 torr – 90.00 torr = 10.0 torr

 

 

 

또는

ΔP = 100.0 torr × (10.0/100) = 10.0 torr

 

 

 

ΔP = X_용질 • P°_용매

( 참고 https://ywpop.tistory.com/2646 )

 

10.0 = (X_용질) (100.0)

 

X_용질 = 10.0 / 100.0 = 0.100

 

 

 

벤젠의 밀도 = 0.8765 g/mL 이고,

C6H6의 몰질량 = 6(12) + 6(1) = 78 g/mol 이므로,

100.0 mL benzene의 몰수를 계산하면,

 

(100.0 mL) (0.8765 g/mL) (1 mol / 78 g)

= (100.0) (0.8765) (1 / 78) = 1.1237 mol benzene (용매)

 

 

 

용질의 몰수를 계산하면,

0.100 = x / (x + 1.1237)

( 참고: 몰분율 https://ywpop.tistory.com/2659 )

 

0.100x + 0.11237 = x

 

(1 – 0.100)x = 0.11237

 

x = 0.11237 / (1 – 0.100)

= 0.1249 mol solute

 

 

 

답: (c) 0.1248

 

 

 

 

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