The vapour pressure of pure benzene is 639.7mm of Hg and vapour pressure of solution of a solute in benzene is 631.9mm of Hg. Calculate the molality of solution.

Asked by pravinbgsbihar | 24th Feb, 2021, 08:17: PM

Expert Answer:

straight X subscript straight a space equals space fraction numerator straight P subscript 0 minus straight P over denominator straight P subscript 0 end fraction space space equals space space fraction numerator 639.7 minus 631.9 over denominator 639.7 end fraction space equals space 1.22 space cross times 10 to the power of negative 2 end exponent

straight m equals fraction numerator straight n over denominator straight w subscript straight s space end fraction rightwards double arrow straight w subscript straight s equals straight n over straight m

straight n subscript straight s space equals space straight w subscript straight s over straight M subscript straight s space equals space straight n over straight M subscript straight s

straight X subscript straight a space equals space fraction numerator straight n over denominator straight n subscript straight s plus space straight n end fraction space equals space fraction numerator 1 over denominator 1 plus begin display style 1 over mM subscript straight s end style end fraction comma space straight M subscript straight s equals 78 space straight g

1 plus 1 over mM subscript straight s space equals space 1 over straight X subscript straight a

1 over mM subscript straight s space equals space 1 over straight X subscript straight a minus 1 space equals space fraction numerator 1 minus straight X subscript straight a over denominator straight X subscript straight a end fraction

mM subscript straight s equals fraction numerator straight X subscript straight a over denominator 1 minus straight X subscript straight a end fraction space
straight m space equals space fraction numerator straight X subscript straight a over denominator left parenthesis 1 minus straight X subscript straight a right parenthesis. straight M subscript straight s end fraction
Now comma space on space putting space values space we space get comma space straight m equals 0.156 space straight m.

Answered by Ramandeep | 25th Feb, 2021, 03:08: PM