InterviewSolution
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InterviewSolution
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A certain mass of a substance when dissolved in 100g C_(6)H_(6) lowers the freezing point by 1.28^(@)C. The same mass of solute dissolved in 100g of water lowers the freezing point by 1.40^(@)C. If substance has normal molecular mass in benzene and is completely dissociated in water, into how many ions does it dissociate in water, K_(f) for H_(2)O and C_(6)H_(6) are 1.86 and 5.12 K mol^(-1) kg respectively |
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Answer» For the solution in BENZENE using the data given `1.28=(1000xx5.12xx w)/(m_(N)XX100)` (`m_(N)` = normal mol. mass) ……(i) For the solution in water in which solute dissociates `1.40=(1000xx1.86xx w)/(m_(esp.)xx100)`.......(ii) Dividing eq. (ii) by (i). `i=(m_(N))/(m_(EXP.))=(1.40)/(1.28)xx(5.12)/(1.86)=3.01~~3.0` Now, suppose that formula for solute is `{:(A_(x)B_(y),hArr,xA^(+),+,yB^(-)),(1,,0,,0),((1-alpha),,x alpha,,y alpha):}` `therefore i=1-alpha+x alpha+y alpha` `because` i=3 and `alpha = 1`(Given that `alpha = 1`) `therefore` No. of ions given (x+y)=3 |
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