Question

24. The difference between heats of reaction at constant
pressure and constant volume for the reaction
2CH (1) + 150,(g) — 1200,(g) + 6H2O(l) at
25°C in KJ is
(1) + 7.43
T2) +3.72
(3) -7.43
(4) - 3.72​

Answer 1

Answer:

1) +7.43kj

Explanation:

The heat of reaction is basically ΔH at constant pressure and is ΔU at constant volume.

Since, for any reaction the relation between this heats is given by equation,

ΔH = ΔU + (Δn

g

)RT

where, Δn

g

= change in number of gaseous moles in any reaction.

Since, in the above reaction the only gaseous species are CO

2

and O

2

, so,

Δn

g

=12−15=−3.

Hence, using ΔH - ΔU = (Δn

g

)RT

ΔH - ΔU =(−3)RT=(−3)×8.314×298.15J (T in Kelvin)

=> ΔH - ΔU=7430J=7.43KJ