If bond enthalpies of $N \equiv N$,$H - H$ and $N - H$ bonds are $x_1, x_2$ and $x_3$ respectively,$\Delta H_f^o$ for $NH_3$ will be

The enthalpy change $(\Delta H)$ for the neutralisation of $1 \ M \ HCl$ by caustic potash in dilute solution at $298 \ K$ is ..... $kJ$.

At $298 \ K$, the enthalpy change (in $kJ$) for the reaction given below is: $CH_{4(g)} + O_{2(g)} \rightarrow C_{(s)} + 2H_2O_{(l)}$
Given:
$1) \ H_{2(g)} + \frac{1}{2}O_{2(g)} \rightarrow H_2O_{(l)} ; \Delta H^{\ominus} = -286 \ kJ$
$2) \ C_{(s)} + O_{2(g)} \rightarrow CO_{2(g)} ; \Delta H^{\ominus} = -394 \ kJ$
$3) \ CH_{4(g)} + 2O_{2(g)} \rightarrow CO_{2(g)} + 2H_2O_{(l)} ; \Delta H^{\ominus} = -890 \ kJ$

Combustion of $1$ $mol$ of benzene is expressed as:
$C_6H_{6(l)} + \frac{15}{2} O_{2(g)} \rightarrow 6CO_{2(g)} + 3H_2O_{(l)}$
The standard enthalpy of combustion of $2$ $mol$ of benzene is $-x$ $kJ$.
$x = . . . . . . . . . .$
$(1)$ Standard enthalpy of formation of $1$ $mol$ of $C_6H_{6(l)}$ is $48.5$ $kJ \ mol^{-1}$.
$(2)$ Standard enthalpy of formation of $1$ $mol$ of $CO_{2(g)}$ is $-393.5$ $kJ \ mol^{-1}$.
$(3)$ Standard enthalpy of formation of $1$ $mol$ of $H_2O_{(l)}$ is $-286$ $kJ \ mol^{-1}$.

The enthalpy changes for the following processes are listed below:

$Cl_{2(g)} \rightarrow 2Cl_{(g)}$	$242.3 \ kJ \ mol^{-1}$
$I_{2(g)} \rightarrow 2I_{(g)}$	$151.0 \ kJ \ mol^{-1}$
$ICl_{(g)} \rightarrow I_{(g)} + Cl_{(g)}$	$211.3 \ kJ \ mol^{-1}$
$I_{2(s)} \rightarrow I_{2(g)}$	$62.76 \ kJ \ mol^{-1}$

Given that the standard states for iodine and chlorine are $I_{2(s)}$ and $Cl_{2(g)}$,the standard enthalpy of formation for $ICl_{(g)}$ is : ............... $kJ \ mol^{-1}$

When $4 \ g$ of iron is burnt to ferric oxide at constant pressure,$29.28 \ kJ$ of heat is evolved. What is the enthalpy of formation of ferric oxide in $kJ \ mol^{-1}$? (At. Wt. of $Fe = 56$)