Assume each reaction is carried out in an open container. For which reaction will ΔH = ΔE?

• H₂ (g) + Br₂ (g) →2HBr (g)

• C (s) + 2 H₂O (g) → 2 H₂ (g) + CO₂ (g)

• PCl₅ (g) →PCl₃ (g) + Cl₂ (g) 

• 2CO (g) + O₂ (g) → 2 CO₂ (g)

A.

H₂ (g) + Br₂ (g) →2HBr (g)

As we know that
 ΔH = ΔE + PΔV
ΔH = ΔE +ΔnRT ..(1)
where ΔH → change in enthalpy of the system (standard heat at constant pressure)
Δ E → change in internal energy of system (Standard heat at constant volume)
Δn → no. of gaseous moles of product - no. of gaseous moles of reactant
R → gas constant
T → absolute temperature
If Δ n = 0 for reactions which is carried out in an open container, therefore, Δn = 0 for reactions which are carried out in an open container, therefore, ΔH  =ΔE
so for reaction (1) Δn = 2-2 = 0
Hence, for reaction (1) , ΔH =ΔE