Calculate the standard enthalpy change for the following reaction,
$2\text{C}_2\text{H}_6\text{(g)} + 7\text{O}_2\text{(g)} \longrightarrow 4\text{CO}_2\text{(g)} + 6\text{H}_2\text{O}\text{(l)}$
Given, $\Delta_f H^\circ(\text{C}_2\text{H}_6) = -85\ \text{kJ mol}^{-1}$
$\Delta_f H^\circ(\text{CO}_2) = -390\ \text{kJ mol}^{-1}$
$\Delta_f H^\circ(\text{H}_2\text{O}) = -285\ \text{kJ mol}^{-1}$

The solubility of salt $\text{AX}_2$ is $6 \times 10^{-12}\ \text{mol dm}^{-3}$. What is solubility product of the salt ?

An organic monobasic acid has dissociation constant $1.96 \times 10^{-8}$. What is its percentage dissociation in $0.01$ M solution ?

Which of the following aqueous salt solutions has the least pH value ?