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The entropy of vaporisation of a liquid ...

The entropy of vaporisation of a liquid is `58 JK^(-1) mol^(-1)` . If 100 g of its vapour condenses at its boiling point of `123^(@) C,` the value of entropy change for the process is

A

`-100 JK ^(-1)`

B

`100 JK ^(-1)`

C

`- 123 JK ^(-1)`

D

`123 JK ^(-1)`

Text Solution

Verified by Experts

The correct Answer is:
A
Given entropy of vaprisation `= 58 JK ^(-1) mol ^(-1)`
i.e., entropy change when 1 mole of the liquid vapourises `= 58 JK ^(-1)`
`therefore `Enthropy change when 1 mole of the liguid condenes `= - 58 JK ^(-1) (because` Condensation and vaporisation are opposite process).
Moles of the liquid used in the reaction
`= (100)/(58) =1. 72mol`
`therefore` Entropy change when `1.72` mole (or 100g) of the liquid condenses
`= (-5xx 1. 72)/(1) = - 100 JK ^(-1) `
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