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Please help! - Physical and Chemical Equilibria - BITSAT

An 0.8M solution of ethanol has density 0.99gcm^{-3}. The molality of the solution is

  • Option 1)

    0.8

  • Option 2)

    Less than 0.8

  • Option 3)

    0.84

  • Option 4)

    0.4

 
Answers (1)
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As learnt in

Molality -

Molality = \frac{Moles \: of \: solute}{Mass \, \: o\! f\: solution(Kg)}

-

 

 We know, m = \frac{1000M}{1000\ d - Mm_{1}}

m1 = molar mass of solute

M = Molarity

d = density of solution

m = molality

\therefore  we have, m = \frac{1000 \times 0.8}{1000\times 0.99-0.8\times 46}

                            = 0.84


Option 1)

0.8

This answer is incorrect

Option 2)

Less than 0.8

This answer is incorrect

Option 3)

0.84

This answer is correct

Option 4)

0.4

This answer is incorrect

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