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

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

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

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

Consider the cell

$$\mathrm{Pt(s)|{H_2}(g)\,(1\,atm)|{H^ + }\,(aq,[{H^ + }] = 1)||F{e^{3 + }}(aq),F{e^{2 + }}(aq)|Pt(s)}$$

Given $$\mathrm{E_{F{e^{3 + }}/F{e^{2 + }}}^o = 0.771\,V}$$ and $$\mathrm{E_{{H^ + }/1/2\,{H_2}}^o = 0\,V,\,T = 298\,K}$$

If the potential of the cell is 0.712 V, the ratio of concentration of Fe$$^{2+}$$ to Fe$$^{3+}$$ is _____________ (Nearest integer)

The osmotic pressure of solutions of PVC in cyclohexanone at 300 K are plotted on the graph.

The molar mass of PVC is ____________ g mol$$^{-1}$$ (Nearest integer)

(Given : R = 0.083 L atm K$$^{-1}$$ mol$$^{-1}$$)

In sulphur estimation, 0.471 g of an organic compound gave 1.4439 g of barium sulphate. The percentage of sulphur in the compound is ____________ (Nearest Integer)

(Given : Atomic mass Ba: 137 u, S: 32 u, O: 16 u)