$250 \ mL$ of a sodium carbonate solution contains $2.65 \ g$ of $Na_2CO_3$. If $10 \ mL$ of this solution is diluted to $1 \ L$,what is the concentration of the resultant solution (in $M$)?

$A$ pre-weighed vessel was filled with oxygen at $N.T.P.$ and weighed. It was then evacuated,filled with $SO_2$ at the same temperature and pressure,and again weighed. The weight of oxygen will be

$1 \ L$ of $N_2$ and $\frac{7}{8} \ L$ of $O_2$ gases are mixed at the same temperature and pressure. What is the relationship between their masses in the mixture?

How many moles of potassium chlorate $(KClO_3)$ must be heated to obtain $11.2 \ L$ of oxygen at $NTP$?

How many grams of a dibasic acid (molar mass $= 200$) are present in $100 \, mL$ of its aqueous solution to make its strength $0.1 \, N$ (decinormal)?

The number of chlorine atoms in $20 \, mL$ of chlorine gas at $STP$ is ..... $\times 10^{21}$. (Round off to the Nearest Integer).
[Assume chlorine is an ideal gas at $STP$,$R = 0.083 \, L \, bar \, mol^{-1} \, K^{-1}$,$N_{A} = 6.023 \times 10^{23}$]