Following data is known about the melting of a compound $AB$: $\Delta H = 9.2 \ kJ \ mol^{-1}$,$\Delta S = 0.008 \ kJ \ K^{-1} \ mol^{-1}$. Its melting point is:

$4 \ g$ of $NH_4NO_3$ were dissolved in $196 \ g$ of water at constant pressure in a calorimeter with a heat capacity of $160 \ J \ K^{-1}$. The temperature fell by $1.3 \ K$. The specific heat of the solution is $4.2 \ J \ K^{-1} \ g^{-1}$. The enthalpy of solution of $NH_4NO_3$ is $......$ $kJ \ mol^{-1}$.

$C_{(s)} + O_{2(g)} \rightarrow CO_{2(g)} + 400 \; kJ$
$C_{(s)} + \frac{1}{2} O_{2(g)} \rightarrow CO_{(g)} + 100 \; kJ$
When coal of purity $60 \%$ is allowed to burn in the presence of insufficient oxygen,$60 \%$ of carbon is converted into $CO$ and the remaining is converted into $CO_2$.
The heat generated when $0.6 \; kg$ of coal is burnt is (in $; kJ$)

The heat of vaporisation and heat of fusion of $H_2O$ are $540 \, cal/g$ and $80 \, cal/g$. The ratio of $\frac{\Delta S_{vap}}{\Delta S_{fusion}}$ for water is :-

$1 \, mol$ of oxygen gas is heated at constant volume from $20 \, ^oC$ to $30 \, ^oC$. What will be the change in the internal energy of the gas? Given the molar heat capacity of oxygen at constant pressure,$C_P = 7.03 \, cal \, mol^{-1} \, K^{-1}$ and $R = 2 \, cal \, mol^{-1} \, K^{-1}$. (Answer in $cal$)

Which graph represents an exothermic reaction?