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Question: \(\Delta U^{o}\) of combustion of \(CH_{4(g)}\)at certain temperature is \(- 393kJmol^{- 1}\) The va...

ΔUo\Delta U^{o} of combustion of CH4(g)CH_{4(g)}at certain temperature is −393kJmol−1- 393kJmol^{- 1} The value of ΔHo\Delta H^{o} is

A

Zero

B

<ΔUo< \Delta U^{o}

C

>ΔUo> \Delta U^{o}

D

Equal to ΔUo\Delta U^{o}

Answer

<ΔUo< \Delta U^{o}

Explanation

Solution

: The balanced equation for combustion of methane is.

CH4(g)+2O2(g)→CO2(g)+2H2O(l)CH_{4(g)} + 2O_{2(g)} \rightarrow CO_{2(g)} + 2H_{2}O_{(l)}

Here, Δng=1−3=−2\Delta n_{g} = 1 - 3 = - 2

ΔHo−ΔUo+ΔngRT\Delta H^{o} - \Delta U^{o} + \Delta n_{g}RT

ΔHo=−393−2RT\Delta H^{o} = - 393 - 2RT

∴ΔHo<ΔUo\therefore\Delta H^{o} < \Delta U^{o}