$250 \ mL$ 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 $M$)?

What is $\Delta n$ for the combustion of $1 \ mole$ of benzene,when both the reactants and the products are in the gaseous state at $298 \ K$?

$100 \, mL$ of $Na_{3}PO_{4}$ solution contains $3.45 \, g$ of sodium. The molarity of the solution is $..... \times 10^{-2} \, mol \, L^{-1}$ $(Nearest \, integer)$.
[$Atomic \, Masses - Na: 23.0 \, u, O: 16.0 \, u, P: 31.0 \, u$]

$X$ litres of carbon monoxide is present at $STP$. It is completely oxidized to $CO_2$. The volume of $CO_2$ formed is $11.207$ litres. What is the value of $X$ in litres?

If the reduction of a sample of $Cu_2O$ yields $1.27 \, g$ of $Cu$,then how many grams of oxygen must be present in it?

What is the value of percent atom economy when an organic compound of formula weight $75 \ u$ is obtained from reactants having sum formula weight $225 \ u$?