Question

For the reaction H₂ + I₂ ⇋ 2HI, ΔH and ΔU are related as
1. ΔH > ΔU
2. ΔH < ΔU
3. ΔH = ΔU
4. Can't say

Answer 1

Correct Answer - Option 3 : ΔH = ΔU

The correct answer is ΔH = ΔU.

As we know,

⇒ΔH = ΔU + Δn_g​RT

Here, 

⇒H₂​(g) + I₂(g) ⟶ 2HI(g) 

⇒Δn_g = 0 [ Δng = no of gaseous product - no of gaseous reactant] which is 2 - (1 + 1) = 0

so, ΔH =ΔU

• Isolated System – An isolated system cannot exchange both energy and mass with its surroundings.
  • The universe is considered an isolated system.
• Closed System – Across the boundary of the closed system, the transfer of energy takes place but the transfer of mass doesn’t take place.
  • Refrigerator, compression of gas in the piston-cylinder assembly are examples of closed systems.
• Open System – In an open system, the mass and energy both may be transferred between the system and surroundings.
  • A steam turbine is an example of an open system.
• There are four types of thermodynamic process that have their unique properties, and they are:
  • Adiabatic Process – A process where no heat transfer into or out of the system occurs.
  • Isochoric Process – A process where no change in volume occurs and the system does no work.
  • Isobaric Process – A process in which no change in pressure occurs.
  • Isothermal Process – A process in which no change in temperature occurs.