The enthalpy change for chemical reaction is denoted aas `DeltaH^(Theta)` and `DeltaH^(Theta) = H_(P)^(Theta) - H_(R)^(Theta)`. The relation between enthalpy and internal enegry is expressed by equation:
`DeltaH = DeltaU +DeltanRT`
where `DeltaU =` change in internal enegry `Deltan =` change in number of moles, `R =` gas constant.
`H_(2)(g) +((1)/(2))O_(2)(g) = H_(2)O(l), DeltaH_(298K) = - 68.00kcal`
Heat of voporisation of water at `1` atm and `25^(@)C` is `10.00 kcal`. The standard heat of formation (in kcal) of `1` amol vapour a `25^(@)C` is

Options

A. `-78.00`
B. `78.00`
C. `+58.00`
D. `-58.00`

Explanation

`{:(H_(2)(g)+(1)/(2)O_(2)rarrH_(2)O(1), DeltaH=-68.00kcal),(H_(2)O(l)rarrH_(2)O(g),DeltaH =10.0kcal),(ulbar("On addition"H_(2)(g)+(1)/(2)O_(2)rarrH_(2)O(g),DeltaH =-58.0kcal)):}`