1 gram of sodium hydroxide was treated with $$25 \mathrm{~mL}$$ of $$0.75 \mathrm{~M} \mathrm{~HCl}$$ solution, the mass of sodium hydroxide left unreacted is equal to

The highest number of helium atoms is in

A compound X contains $$32 \%$$ of A, $$20 \%$$ of B and remaining percentage of C. Then, the empirical formula of $$\mathrm{X}$$ is :

(Given atomic masses of A=64 ; B=40 ; C=32 u)

The density of 1 M solution of a compound 'X' is 1.25 g mL$$^{-1}$$. The correct option for the molality of solution is (Molar mass of compound X = 85 g):