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NEET 2023
Exam
NEET
Year
2023
Subject
Chemistry
Chapter
Thermodynamics (C)

NEET 2023 · Chemistry · Thermodynamics (C)

Which amongst the following options is the correct relation between...

Which amongst the following options is the correct relation between change in enthalpy and change in internal energy?

Options

  1. A∆H+∆U=∆ngR∆ H + ∆ U = ∆ {n}_{g}R
  2. B∆H=∆U−∆ngRT∆ H = ∆ U - ∆ {n}_{g}RT
  3. C∆H=∆U+∆ngRT∆ H = ∆ U + ∆ {n}_{g}RT
  4. D∆H−∆U=−∆ngRT∆ H - ∆ U = - ∆ {n}_{g}RT

Correct answer

C. ∆H=∆U+∆ngRT∆ H = ∆ U + ∆ {n}_{g}RT

Step-by-step solution

Correct relation between change in enthalpy and change in internal energy is

∆H=∆U+∆ngRT∆ H = ∆ U + ∆ {n}_{g}RT

As we know,

∆H=∆U+P∆V....(i)∆ H = ∆ U + P ∆ V . . . . ( i )

For an ideal gas

PV=nRTPV = nRT

For reactant, PVA=nART{PV}_{A} = {n}_{A}RT

For product, PVB=nBRT{PV}_{B} = {n}_{B}RT

Thus,

P(VB−VA)=(nB−nA)RTP∆V=∆ngRT......(ii)P ( {V}_{B} - {V}_{A} ) = ( {n}_{B} - {n}_{A} ) RTP ∆ V = ∆ {n}_{g}RT . . . . . . ( ii )

Substituting (ii) in (i), we get

∴∆H=∆U+∆ngRT∴ ∆ H = ∆ U + ∆ {n}_{g}RT

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