Molar mass of the salt from $$\mathrm{NaBr}, \mathrm{NaNO}_3, \mathrm{KI}$$ and $$\mathrm{CaF}_2$$ which does not evolve coloured vapours on heating with concentrated $$\mathrm{H}_2 \mathrm{SO}_4$$ is ________ $$\mathrm{g} \mathrm{~mol}{ }^{-1}$$.

(Molar mass in $$\mathrm{g} \mathrm{~mol}^{-1}: \mathrm{Na}: 23, \mathrm{~N}: 14, \mathrm{~K}: 39, \mathrm{O}: 16, \mathrm{Br}: 80, \mathrm{I}: 127, \mathrm{~F}: 19, \mathrm{Ca}: 40)$$

The mass of sodium acetate $$\left(\mathrm{CH}_3 \mathrm{COONa}\right)$$ required to prepare $$250 \mathrm{~mL}$$ of $$0.35 \mathrm{~M}$$ aqueous solution is ________ g. (Molar mass of $$\mathrm{CH}_3 \mathrm{COONa}$$ is $$82.02 \mathrm{~g} \mathrm{~mol}^{-1}$$)

$$0.05 \mathrm{~cm}$$ thick coating of silver is deposited on a plate of $$0.05 \mathrm{~m}^2$$ area. The number of silver atoms deposited on plate are ________ $$\times 10^{23}$$. (At mass $$\mathrm{Ag}=108, \mathrm{~d}=7.9 \mathrm{~g} \mathrm{~cm}^{-3}$$)

If $$50 \mathrm{~mL}$$ of $$0.5 \mathrm{M}$$ oxalic acid is required to neutralise $$25 \mathrm{~mL}$$ of $$\mathrm{NaOH}$$ solution, the amount of $$\mathrm{NaOH}$$ in $$50 \mathrm{~mL}$$ of given $$\mathrm{NaOH}$$ solution is ______ g.