Question

Enthalpy changes that are difficult to measure directly can often be determined using Hess’ Law
to construct an enthalpy cycle.
Which enthalpy change is indicated by X in the enthalpy cycle shown?

A–4 ×the enthalpy of combustion of hydrogen
B+4 ×the enthalpy of combustion of hydrogen
C–2 ×the enthalpy of formation of water
D+2 ×the enthalpy of formation of water

Answer 1

Which one do u think?

Answer 2

The standard enthalpy change of combustion of a compound is the enthalpy change which occurs when one mole of the compound is burned completely in oxygen under standard conditions, and with everything in its standard state.
The standard enthalpy change of formation of a compound is the enthalpy change which occurs when one mole of the compound is formed from its elements under standard conditions, and with everything in its standard state.
I go with Choice D but i am not sure