Question

Change in enthalpy and change in internal energy are equal at room temperature for:

• A. combustion of glucose
• B. combustion of ethylene
• C. combustion of methane
• D. combustion of ethyl alcohol

Answer 1

The correct option is A combustion of glucose

$6O_2\left(g\right)+C_6{H}_{12}{O}_6\left(s\right)\to 6C{O}_2\left(g\right)+6H_{2}O\left(l\right)$

$\Delta n_g=0$ for combustion of glucose

$\Delta H=\Delta E+\Delta n_{g}RT$

$\Delta n_g=0$

$\therefore \Delta H=\Delta E$

i.e. Change in enthalpy $=$ change in internal energy.