Volume of $$3 \mathrm{M} \mathrm{~NaOH}$$ (formula weight $$40 \mathrm{~g} \mathrm{~mol}^{-1}$$ ) which can be prepared from $$84 \mathrm{~g}$$ of $$\mathrm{NaOH}$$ is __________ $$\times 10^{-1} \mathrm{dm}^3$$.

Mass of methane required to produce $$22 \mathrm{~g}$$ of $$\mathrm{CO}_2$$ after complete combustion is _______ g.

(Given Molar mass in g mol-1 $$\mathrm{C}=12.0$$, $$\mathrm{H}=1.0$$, $$\mathrm{O}=16.0)$$

$$1 \mathrm{~g}$$ of a carbonate $$\left(\mathrm{M}_{2} \mathrm{CO}_{3}\right)$$ on treatment with excess $$\mathrm{HCl}$$ produces $$0.01 \mathrm{~mol}$$ of $$\mathrm{CO}_{2}$$. The molar mass of $$\mathrm{M}_{2} \mathrm{CO}_{3}$$ is __________ $$\mathrm{g} ~\mathrm{mol}^{-1}$$. (Nearest integer)