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An aqueous solution of 2% non-volatile s | Class 12 Chemistry Chapter Solutions, Solutions NCERT Solutions

Question:

An aqueous solution of 2% non-volatile solute exerts a pressure of 1.004 bar at the normal boiling point of the solvent. What is the molar mass of the solute?

Answer:

Here,

Vapour pressure of the solution at normal boiling point (p₁) = 1.004 bar (Given)

Vapour pressure of pure water at normal boiling point (p₁⁰) = 1.013 bar

Mass of solute, (w₂) = 2 g

Mass of solvent (water), (w₁) = 100 - 2 = 98 g

Molar mass of solvent (water), (M₁) = 18 g mol^{- 1}

According to Raoult's law,

(p₁⁰ - p₁) / p₁⁰= (w₂x M₁) / (M₂x w₁ )

(1.013 - 1.004) / 1.013 = (2 x 18) / (M₂ x 98 )

0.009 / 1.013 = (2 x 18) / (M₂ x 98 )

M₂ = (2 x 18 x 1.013) / (0.009 x 98)

M₂ = 41.35 g mol^{- 1}

Hence, the molar mass of the solute is 41.35 g mol^{- 1}.

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Comments

nishant
2021-07-14 10:21:40

there is a little mistake in formula right formula is (p1* - p1) / p1 = (w2 x M1 ) / (M2 x w1 ) by this formula the answer is 40.9 which is correct also mention in NCERT question 2.15

Reena Roy
2019-07-18 16:08:54

Very helpful

Anupama
2019-07-06 17:49:54

In the question,it's only given as a solvent.Why did u take it as water?

Veer Pratap Singh Laungwal
2019-05-30 10:16:09

Thank you so much very informative

Satya prakash satapathy
2019-05-26 08:25:27

Thanks

Pooja
2019-05-22 01:01:14

Thx

Arushi
2019-05-05 20:41:39

Thanks

pratap
2019-05-05 08:52:22

isme vapour presure water ka to diya hi na h

Kr shiddartha
2019-04-23 22:24:47

Thanks

Prashant
2019-04-21 11:36:46

Thanks

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Welcome to the NCERT Solutions for Class 12 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 2 , Question 15: An aqueous solution of 2% non-volatile solute exerts a pressure of 1.004 bar at the normal boiling p....

An aqueous solution of 2% non-volatile s | Class 12 Chemistry Chapter Solutions, Solutions NCERT Solutions

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