The standard enthalpies of formation of $C{O}_2\left(g\right),H_{2}O\left(l\right)$  and glucose(s) at ${25}^{0}C$ are $-400kJ/mol,-300kJ/mol$  and $-1300kJ/mole$  respectively. The standard enthalpy of combustion per gram of glucose at ${25}^{0}C$  is

The standard enthalpy of the combustion of glucose can be calculated by the eqn. 
 $C_6{H}_{12}{O}_6\left(s\right)+6O_2\left(g\right)\to 6C{O}_2\left(g\right)+6H_{2}O\left(1\right)$
 $\Delta H_C=6\times \Delta H_f\left(C{O}_2\right)+6\times \Delta H_f\left(H_{2}O\right)-\Delta H_f\left[C_6{H}_{12}{O}_6\right]$
 $\Delta H^0=6(-400)+6(-300)-(-1300)=-2900kJ/mol$
For one gram of glucose, enthalpy of combustion 
 $\Delta H^0=-\frac{2900}{180}=-16.11kJ/g$