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

B

Explanation

Applying Hess.s law
`C_((g)) + O_(2) rarr CO_(2(g)) x kJ mol^(-1)` ....(i)
`C_((s)) + (1)/(2) O_(2) rarr CO_((g)) y kJ mol^(-1)` ...(ii)
`bar(O_(2)- (1)/(2) O_(2(g)) rarr CO_(2(g)) - CO_((g)) z kJ mol^(-1))` ....(iii)
On subtracting eq (i) and (ii) we get
`CO_((g)) + (1)/(2) O_(2(g)) rarr CO_(2(g))`
`therefore x- y= z`
`x= y+ z`