Given :
(i) `C("graphite") + O_(2)(g) rarr CO(g) ,Delta_(r )H^(@) = xkJ mol^(-1)`
(ii) `C("graphite") + 1/2 O_(2)(g) rarr CO_(2)(g), Delta_(r )H^(@) = ykJ mol^(-1)`
(iii) `CO(g) + 1/2 O_(2)(g) rarr CO_(2)(g) , Delta_(r )H = z kJ mol^(-1)`
Based on the above thermochemical equations, find out which one of the following algebraic relationships is correct ?

Options

A. z=x+y
B. x=y+z
C. y=2z-x
D. x=y-z

Answer

D

Explanation

Applying Hess's law
`C_((g))+O_(2)rarrCO_(2(g))" x kJ mol"^(-1)" ....(i)"`
`{:(ul(C_((s))+(1)/(2)O_(2)rarrCO_((g))" y kJ mol"^(-1) )" ...(ii)"),(O_(2)-(1)/(2)O_(2(g))rarrCO_(2(g))-CO_((g))z kJ mol^(-1)" ....(iii)"):}`
On substracting eq. (i) and (ii) we get
`CO_((g))+(1)/(2)O_(2(g))rarrCO_(2(g)) thereforex-y=zimpliesx=y+z`