For the gas phase reaction,$PCl_{5(g)} \rightleftharpoons PCl_{3(g)} + Cl_{2(g)}$,which of the following conditions are correct?

Which of the following is/are true about the reversible isothermal expansion of an ideal gas?
$(a) \ \Delta U = 0$
$(b) \ q = 0$
$(c) \ \Delta T = 0$
$(d) \ q = 2.303 \ nRT \ \log_{10} \left( \frac{V_2}{V_1} \right)$

$\Delta H^o_f$ of water is $-285.5 \, kJ \, mol^{-1}$. If enthalpy of neutralisation of monoacidic strong base is $-57.3 \, kJ \, mol^{-1}$,$\Delta H^o_f$ of $OH^{-}$ ion will be.....$kJ \, mol^{-1}$

$4 \ g$ 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 $......$ $kJ \ mol^{-1}$.

Which graph represents an exothermic reaction?

Calculate $\Delta H_f^o$ of $SiH_2$ from the following reactions:
$Si_2H_{6(g)} + H_{2(g)} \to 2SiH_{4(g)}, \Delta H = -11.7 \ kJ/mol$
$SiH_{4(g)} \to SiH_{2(g)} + H_{2(g)}, \Delta H = +239.7 \ kJ/mol$
$\Delta H_f^o(Si_2H_{6(g)}) = 80.3 \ kJ/mol$