$$600 \mathrm{~mL}$$ of $$0.01~\mathrm{M} ~\mathrm{HCl}$$ is mixed with $$400 \mathrm{~mL}$$ of $$0.01~\mathrm{M} ~\mathrm{H}_{2} \mathrm{SO}_{4}$$. The $$\mathrm{pH}$$ of the mixture is ___________ $$\times 10^{-2}$$. (Nearest integer)

[Given $$\log 2=0.30$$

$$\log 3=0.48$$

$$\log 5=0.69$$

$$\log 7=0.84$$

$$\log 11=1.04]$$

Millimoles of calcium hydroxide required to produce 100 mL of the aqueous solution of pH 12 is $$x\times10^{-1}$$. The value of $$x$$ is ___________ (Nearest integer).

Assume complete dissociation.

A litre of buffer solution contains 0.1 mole of each of NH$$_3$$ and NH$$_4$$Cl. On the addition of 0.02 mole of HCl by dissolving gaseous HCl, the pH of the solution is found to be _____________ $$\times$$ 10$$^{-3}$$ (Nearest integer)

[Given : $$\mathrm{pK_b(NH_3)=4.745}$$

$$\mathrm{\log2=0.301}$$

$$\mathrm{\log3=0.477}$$

$$\mathrm{T=298~K]}$$

If the pKa of lactic acid is 5, then the pH of 0.005 M calcium lactate solution at 25$$^\circ$$C is ___________ $$\times$$ 10$$^{-1}$$ (Nearest integer)