MCQ
A fish swimming in water body when taken out from the water body is covered with a film of water of weight $36\, g$. When it is subjected to cooking at $100^{\circ} C$, then the internal energy for vaporization in $kJ mol ^{-1}$ is $......$ [nearest integer]

[Assume steam to be an ideal gas. Given $A _{ vap } H ^{\ominus}$ for water at $373 \,K$ and $1\, bar$ is $41.1 \,kJ\, mol ^{-1} ; R =$ 8.31 $J\,K ^{-1} \,mol ^{-1}$ ]

  • A
    $66$
  • B
    $96$
  • C
    $50$
  • $38$

Answer

Correct option: D.
$38$
d
$H _{2} O (l) \rightarrow H _{2} O\, ( g )$

$n =\frac{36}{18}=2\, mol$

$\Delta U =\Delta H -\Delta n _{ g } RT$

$=41.1-\frac{1 \times 8.31 \times 373}{1000} \,kJ / mol$

$=38\, kJ / mol$

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