A well stoppered thermos flask contains some ice Cubes. This is an example of a 

For the reaction

${\mathrm{N}}_2+3{\mathrm{H}}_2=2{\mathrm{NH}}_3, ∆\mathrm{H}=?$

For an ideal gas, the relation between the enthalpy change and internal energy at constant temperature is given by

If ${\mathrm{C}}_{\left(\mathrm{s}\right)} + {\mathrm{O}}_{2\left(\mathrm{g}\right)} \to {\mathrm{CO}}_{2\left(\mathrm{g}\right)} , ∆\mathrm{H}=\mathrm{X}$ and ${\mathrm{CO}}_{\left(\mathrm{g}\right)} +\frac{1}{2}{\mathrm{O}}_{2\left(\mathrm{g}\right)}\to {\mathrm{CO}}_{2\left(\mathrm{g}\right)}, ∆\mathrm{H}=\mathrm{Y}$ then the heat of formation of $\mathrm{CO}$ is

Enthalpies of elements in their standard states are taken as zero. Hence the enthalpy of formation of a compound

Which of the following values of heat of formation indicates that the product is least stable ?

For an adiabatic process, which of the following is correct.

An exothermic reaction is one which