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 $298 \ K$?

Volume of air needed for complete combustion of $10 \ L$ of $C_2H_4$ is :
$($Assume air contains $20\%$ of $O_2$ by volume$)$ (in $L$)

$250 \ mL$ 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 $M$)?

$A$ mixture of $2.3 \ g$ formic acid and $4.5 \ g$ oxalic acid is treated with conc. $H_2SO_4$. The evolved gaseous mixture is passed through $KOH$ pellets. Weight of the remaining product at $STP$ is .......... $g$.

How many moles of ethene are required to prepare $6.0 \ g$ of ethane by the hydrogenation process (in $mole$)?

$2 \ N - HCl$ will have the same molar concentration as $....... \ N - H_2SO_4$