Question

If `C(s)+O_(2)(g)rarrCO_(2)(g),DeltaH=X` and `CO(g)+1//2O_(2)(g)rarrCO_(2)(g),DeltaH=Y`, then the heat of formation of `CO` is
A. `X+Y`
B. `X-Y`
C. `Y-X`
D. `XY`

Answer 1

Correct Answer - B
`C(s) + O_(2) (g) rarr CO_(2)(g), Delta H = X` ...(1)
`CO_(g) + 1//20_(2)(g) rarr CO_(2)(g), DeltaH = Y` ....(2)
Subtracting equaction (2) from equaction (1), we get
`C(s) + (1)/(2) O_(2)(g) rarr CO_((g)) = 0`
or `C(s) + (1)/(2) O_(2)(g) rarr CO (g), DeltaH = X - Y`
`DeltaH = X - Y = Delta H_(f) (CO) - (0 + 0)`
`Delta H_(4)(CO) = X - Y`