Thermochemical reactions \[C(\text{graphite})+\frac{1}{2}{{O}_{2}}(g)\to CO(g);\,\Delta H=-110.5\,kJ\] \[CO(g)+\frac{1}{2}{{O}_{2}}(g)\to C{{O}_{2}}(g);\,\Delta H=-283.2\,kJ\] From the above reaction, the heat of reaction for \[C(\text{graphite})+{{O}_{2}}(g)\to C{{O}_{2}}(g)\] will be [CPMT 1988; MP PMT 1989]

• A.                 ?  393.7 kJ           
• B.                 + 393.7 kJ
• C.                 ? 172.7 kJ            
• D.                 + 172.7 kJ