Verified Solution • 2025–26 Session moderate

QJEEM17Chb3ae: JEE Main 2017 Chemistry - Class 11 JEEM17Chb3ae Solution: For a reaction, A(g) A( ); H= 3RT. The correct statement for…

For a reaction, A(g) →\to A( ℓ\ell ); Δ\Delta H= −- 3RT.
The correct statement for the reaction is :

Multiple Choice Options

  • A Δ\Delta H = Δ\Delta U ≠\ne O
  • B Δ\Delta H = Δ\Delta U = O
  • C ∣\left| {} \right. Δ\Delta H ∣\left| {} \right. < ∣\left| {} \right. Δ\Delta U ∣\left| {} \right.
  • D ∣\left| {} \right. Δ\Delta H ∣\left| {} \right. > ∣\left| {} \right. Δ\Delta U ∣\left| {} \right.

Step-by-Step Verified Solution

Given reaction,

A(g)   →\to   A( ll ) ;

We know,

Δ\Delta H = Δ\Delta V + Δ\Delta ng RT

Given, Δ\Delta H = −- 3RT

From reaction,

Δ\Delta ng = 0 −- 1 = −1-1

∴   \therefore\,\,\, Δ\Delta H = Δ\Delta U −- RT

⇒\Rightarrow    \,\,\, −- 3RT = Δ\Delta U −- RT

⇒\Rightarrow    \,\,\, Δ\Delta U = −- 2RT

∴   \therefore\,\,\, ∣ΔU∣\left| {\Delta U} \right| = 2RT

and ∣ΔH∣\left| {\Delta H} \right| = 3RT

∴   \therefore\,\,\, ∣ΔH∣\left| {\Delta H} \right| > ∣ΔU∣\left| {\Delta U} \right|

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