Amongst the following the total number of compounds whose aqueous solution turns red litmus paper blue is ___.<br>KCN, $$\text{K}_2\text{SO}_4$$, NaCl, $$\text{Zn(NO}_3)_2$$, $$\text{FeCl}_3$$, $$\text{K}_2\text{CO}_3$$, $$\text{NH}_4\text{NO}_3$$, LiCN

Salts of a strong base and a weak acid hydrolyse to give basic solutions, which turn red litmus blue. These are KCN, $$\text{K}_2\text{CO}_3$$ and LiCN. $$\text{K}_2\text{SO}_4$$ and NaCl are neutral, while $$\text{Zn(NO}_3)_2$$, $$\text{FeCl}_3$$ and $$\text{NH}_4\text{NO}_3$$ are acidic, so the number is 3.