Question

Predict ∆H > ∆U or ∆H = ∆U. (ii) PCl5(g) → PCl3(g) + Cl2(g)

Answer 1

Answer:

Explanation:

WE KNOW ΔH=ΔU+ngrt

here ng=2-1=1

soΔH=ΔU+RT

SO HERE Δ H IS SMALLER THAN ΔU

Answer 2

Answer :

$\dag\:\underline{\boxed{\bf{PCl_{5}\longrightarrow PCl_3+Cl_2}}}$

Relation between ΔH and ΔE is given by

• ΔH = ΔE + (Δn)RT

where,

$\sf{\Delta n = moles\:of\:products - moles\:of\:reactants}$

➝ Δn = n(PCl₃ + Cl₂) - n(PCl₅)

➝ Δn = (1 + 1) - 1

➝ Δn = 2 - 1

➝ Δn = 1

Substituting the value of Δn, we get

➢ ΔH = ΔE + (Δn)RT

➢ ΔH = ΔE + (1)RT

➢ ΔH = ΔE + RT

➢ ΔH > ΔE