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]

If the solubility product of AB₂ is 3.20 $$ \times $$ 10^–11 M³, then the solubility of AB₂ in pure water is _____ $$ \times $$ 10^–4 mol L^–1.
[Assuming that neither kind of ion reacts with water]

A soft drink was bottled with a partial pressure of CO₂ of 3 bar over the liquid at room temperature. The partial pressure of CO₂ over the solution approaches a value of 30 bar when 44 g of CO₂ is dissolved in 1 kg of water at room temperature. The approximate pH of the soft drink is ______ $$ \times $$ 10^–1.
(First dissociation constant of
H₂CO₃ = 4.0 $$ \times $$ 10^–7; log 2 = 0.3; density
of the soft drink = 1 g mL^–1) .