What is the $[OH^{-}]$ in the final solution prepared by mixing $20.0 \ mL$ of $0.050 \ M \ HCl$ with $30.0 \ mL$ of $0.10 \ M \ Ba(OH)_2$? $...... \ M$

$A$ sample of $Na_2CO_3 \cdot H_2O$ weighing $0.62 \ g$ is added to $100 \ mL$ of $0.1 \ N \ (NH_4)_2SO_4$ solution. What will be the nature of the resulting solution?

The pairs of compounds which cannot exist together in aqueous solution are :
$I. NaH_2PO_4$ and $Na_2CO_3$ $II. Na_2CO_3$ and $NaHCO_3$
$III. NaOH$ and $NaH_2PO_4$ $IV. NaHCO_3$ and $NaOH$

What will be the change in acidity if
$(i)$ $CuSO_4$ is added in saturated $(NH_4)_2SO_4$ solution
$(ii)$ $SbF_5$ is added in anhydrous $HF$?

For a concentrated solution of a weak electrolyte ($K_{eq} = $ equilibrium constant) $A_2B_3$ of concentration '$c$',the degree of dissociation '$\alpha$' is

If $20 \, mL$ of $0.25 \, N$ strong acid and $30 \, mL$ of $0.2 \, N$ strong base are mixed,then the resulting solution is