A flask contains 98 mg of $\mathrm{H}_2 \mathrm{SO}_4$. If $3.01 \times 10^{20}$ molecules of $\mathrm{H}_2 \mathrm{SO}_4$ are removed from the flask. The number of moles of $\mathrm{H}_2 \mathrm{SO}_4$ remained in flask is

$$ \left(N_A=6.02 \times 10^{23}\right) $$

0.1 mole of potassium permanganate was heated at $300^{\circ} \mathrm{C}$. What is weight (ing) of the residue? $$ (\mathrm{Mn}=55 \mathrm{u}, \mathrm{~K}=39 \mathrm{u}, \mathrm{O}=16 \mathrm{u}) $$

100 mL of $\frac{M}{10} \mathrm{Ca}\left(\mathrm{NO}_3\right)_2$ and 200 mL of $\frac{M}{10} \mathrm{KNO}_3$ solutions are mixed. What is the normality of resulted solution with respect to $\mathrm{NO}_3^{-}$?

At STP ' $x$ ' $g$ of a metal hydrogen carbonate $\left(M \mathrm{HCO}_3\right)$ (molar mass $84 \mathrm{~g} \mathrm{~mol}^{-1}$ ) on heating gives $\mathrm{CO}_2$, which can completely react with 0.2 moles of MOH (molar mass $40 \mathrm{~g} \mathrm{~mol}^{-1}$ ) to give $\mathrm{MHCO}_3$. The value of ' $x^{\prime}$ is