Suppose reaction A has delta H of -200kj, reaction B has delta H -100kj,?

Question

if C can be written as the reaction of A forward and B reverse what is delta H for C?

Answer 1

Changing the direction of a reaction changes the sign of enthalpy of reaction.

Therefore:

ΔH(C) = ΔH(A) - ΔH(B) = -200kJ - (-100kJ) = -100kJ