Sulphurous acid (H₂SO₃) has Ka₁ = 1.7 $$\times$$ 10^$$-$$2 and Ka₂ = 6.4 $$\times$$ 10^$$-$$8. The pH of 0.588 M H₂SO₃ is __________. (Round off to the Nearest Integer).

Two salts A₂X and MX have the same value of solubility product of 4.0 $$\times$$ 10^$$-$$12. The ratio of their molar solubilities i.e. $${{S({A_2}X)} \over {S(MX)}}$$ = __________. (Round off to the Nearest Integer)

The pH of ammonium phosphate solution, if pk_a of phosphoric acid and pk_b of ammonium hydroxide are 5.23 and 4.75 respectively, is ___________.

The solubility product of PbI₂ is 8.0 $$\times$$ 10^$$-$$9. The solubility of lead iodide in 0.1 molar solution of lead nitrate is x $$\times$$ 10^$$-$$6. mol/L. The value of x is __________. (Rounded off to the nearest integer) [Given $$\sqrt 2 $$ = 1.41]