At $300\mathrm{K}$ , the vapour pressure of a solution containing 1 mole of $n$ -hexane and 3 moles of $\mathrm{n}$ -heptane is $550\mathrm{m}\mathrm{m}$ of $\mathrm{H}\mathrm{g}$ . At the same temperature, if one more mole of $\mathrm{n}$ -heptane is added to this solution, the vapour pressure of the solution increases by $10\mathrm{m}\mathrm{m}$ of $\mathrm{H}\mathrm{g}$ . What is the vapour pressure in $\mathrm{m}\mathrm{m}\mathrm{H}\mathrm{g}$ of $n$ -heptane in its pure state ?

At 25°C the standard emf of cell having reactions involving two electrons change is found to be 0.295 V. The equilibrium constant of the reaction is :

Kindly consider the following 

Which of the following will not give ether as product :-

Which is most reactive towards electrophilic aromatic substitution reaction :-

Which one of the following ions is the most stable in aqueous solution ?

(At. No. Ti = 22, V = 23, Cr = 24, Mn=25)