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For the reaction $2 Cl left parenthesis straight g right parenthesis space rightwards arrow space space Cl subscript 2 left parenthesis straight g right parenthesis comma$ what are the signs of $increment straight H space and space increment straight S.$ ?

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Long Answer Type

252.
Prove that in a reversible process:
∆_(system) ⁺ ∆S_{(surroundings)} = 0
Or
Prove that there is no net change in entropy in a reversible process.

Suppose heat is absorbed by the system reversible and the heat is lost by the surroundings also reversibly (process occurs under complete reversible condition).

If q_rev is the heat absorbed by the system reversibly, then the heat lost by the surroundings will also be q_rev. If the process takes place isothermally at T kelvin, then Entropy change of the system

Entropy change of the surroundings

Hence the total entropy change for the combined system and surroundings will be:

Hence in a reversible process, the net entropy change for the combined system and the surroundings is zero i.e. there is no net change in entropy.

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253.

Prove that in an irreversible process:
∆S_(system) + ∆S_{(surroundings)}> 0

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254.

What do you understand by:
(i) The entropy of fusion?
(ii) The entropy of vapourisation ?

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Short Answer Type

255.

You are given normal boiling points and standard enthalpies of vapourisation. Calculate the entropy of vapourisation of liquids listed below:
Liquid $straight b. straight p. space left parenthesis degree straight C right parenthesis space space space space space space space space space increment straight H subscript vap superscript 0 space end superscript space left parenthesis kJ space mol to the power of negative 1 end exponent right parenthesis$
$space left parenthesis straight a right parenthesis space Ethanol with left parenthesis straight C subscript 2 straight H subscript 5 OH right parenthesis below space space space space space space space space space space space space space space space space space space 78.4 space space space space space space space space space 42.4 space left parenthesis straight b right parenthesis space Toluene with left parenthesis straight C subscript 2 straight H subscript 5 CH subscript 3 right parenthesis below space space space space space space space space space space space space space space space space space space 110.6 space space space space space space space 35.2 space space$

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256.

Calculate the entropy change of n-hexane when 1 mole of it evaporates at 341.7 K(∆H_vap = 29.0 kJ mol^–1).

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257. When one mole of a solid ‘S’ (molecular weight 46) at its melting point is changed into the liquid at the same temperature, an entropy change of 26.4 JK^–1takes place. Calculate the melting point of the solid if its enthalpy of fusion is 0 .1 kJg^–1.

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