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∆Xf UXΘ of formation of CHX4(g) at certain temperature is – 393 kJ mol–1. The value of ∆Xf HXΘ is ______. - Chemistry

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Question

\[\ce{∆_f U^Θ}\] of formation of \[\ce{CH4 (g)}\] at certain temperature is – 393 kJ mol–1. The value of \[\ce{∆_f H^Θ}\] is ______.

Options

  • zero

  • \[\ce{< ∆_f U^Θ}\]

  • \[\ce{> ∆_f U^Θ}\]

  • equal to \[\ce{∆_f U^Θ}\]

MCQ
Fill in the Blanks

Solution

\[\ce{∆_f U^Θ}\] of formation of \[\ce{CH4 (g)}\] at certain temperature is – 393 kJ mol–1. The value of \[\ce{∆_f H^Θ}\] is \[\ce{< ∆_f U^Θ}\].

Explanation:

The balanced equation for the combustion of methane is

\[\ce{CH4 (g) + 2O2 (g) -> CO2 (g) + 2H2O (l)}\]

Therefore, `∆n_g = 1 - 3 = - 2`

\[\ce{∆H_o = ∆U_o + ∆ng}\] RT

\[\ce{∆H_o = - 393 - 2}\] RT

∴ \[\ce{∆H_o < ∆U_o}\]

shaalaa.com
Enthalpy Change, ∆_rH of a Reaction - Reaction Enthalpy - Thermochemical Equations
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Chapter 6: Thermodynamics - Multiple Choice Questions (Type - I) [Page 69]

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NCERT Exemplar Chemistry [English] Class 11
Chapter 6 Thermodynamics
Multiple Choice Questions (Type - I) | Q 6 | Page 69

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