Easy INTEGER +4 / -1 PYQ · JEE Mains 2021

For water at 100$^\circ$ C and 1 bar,

$\Delta$vap H $-$ $\Delta$vap U = _____________ $\times$ 102 J mol$-$1. (Round off to the Nearest Integer)

[Use : R = 8.31 J mol$-$1 K$-$1]

[Assume volume of H2O(l) is much smaller than volume of H2O(g). Assume H2O(g) treated as an ideal gas]

Answer (integer) 31

Solution

H<sub>2</sub>O<sub>(l)</sub> $\rightleftharpoons$ H<sub>2</sub>O<sub>(v)</sub><br><br>$\Delta$H = $\Delta$U + $\Delta$n<sub>g</sub>RT<br><br>For 1 mole waters;<br><br>$\Delta$n<sub>g</sub> = 1<br><br>$\therefore$ $\Delta$n<sub>g</sub>RT = 1 mol $\times$ 8.31 J/mol-k $\times$ 373 K<br><br>= 3099.63 J $\cong$ 31 $\times$ 10<sup>2</sup> J

About this question

Subject: Chemistry · Chapter: Thermodynamics · Topic: Zeroth and First Law

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