60.3℃ benzene vapor pressure 53.3 kPa 500 g 19.0 g 51.5 kPa molar mass

60.3℃ benzene vapor pressure 53.3 kPa 500 g 19.0 g 51.5 kPa molar mass

 

 

60.3℃에서 벤젠의 증기압은 53.3 kPa이다.

500 g 벤젠에 19.0 g 비휘발성 화합물을 녹였더니

증기압이 51.5 kPa로 떨어졌다.

이 화합물의 몰질량을 구하시오.

 

 

The vapor pressure of benzene is 53.3 kPa at 60.3℃, but it fall to 51.5 kPa

when 19.0 g non-volatile organic compound is dissolved in 500 g benzene.

The molar mass of the non-volatile compound is

 

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ΔP_용액 = X_용질 • P°_용매

( 참고 https://ywpop.tistory.com/2646 )

 

X_용질 = ΔP_용액 / P°_용매

= (53.3 – 51.5) / 53.3

= 0.03377

 

 

 

benzene, C6H6의 몰질량 = 78.11 g/mol 이므로,

500 g / (78.11 g/mol) = 6.40 mol benzene (용매)

( 참고 https://ywpop.tistory.com/7738 )

 

 

 

X_용질 = n_용질 / (n_용질 + n_용매)

 

0.03377 = x / (x + 6.40)

 

0.03377(x + 6.40) = x

 

0.03377x + (0.03377)(6.40) = x

 

(1 – 0.03377)x = (0.03377)(6.40)

 

x = (0.03377)(6.40) / (1 – 0.03377)

= 0.22368 mol

---> 용질의 몰수

 

 

 

화합물의 몰질량을 계산하면,

19.0 g / 0.22368 mol = 84.94 g/mol

 

 

 

답: 85 g/mol

 

 

 

 

[키워드] The vapor pressure of benzene is 53.3 kPa at 60.6℃, but it fell to 51.5 kPa when 19.0 g non-volatile organic compound was dissolved in 500 g benzene. The molar weight of benzene is 78.11 g/mol. Calculate the molar mass of the compound.