Standard enthalpy of combustion of graphite at 25 oC is –393.51 kJ mol -1 and that of diamond
is –395.41 kJ mol-1
. The enthalpy change for graphite is:
A) – 1.91 C) –2.1
B) +2.1 D) +1.91

the answer would be b i believe

50.23 i believe is correct but don't quote me on that.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.