The molarity of a $NaOH$ solution prepared by dissolving $4 \ g$ of it in $250 \ mL$ of water is: (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 .......... $g$.

For preparing a $0.1 \ N$ solution of a compound from its impure sample,where the percentage purity is known,the weight of the substance required will be:

The volume of $0.1 \, N$ dibasic acid sufficient to neutralize $1 \, g$ of a base that furnishes $0.04 \, mole$ of $OH^{-}$ in aqueous solution is ............ $mL$

Chlorine is prepared in the laboratory by treating manganese dioxide $(MnO_{2})$ with aqueous hydrochloric acid according to the reaction
$4HCl_{(aq)} + MnO_{2(s)} \rightarrow 2H_{2}O_{(l)} + MnCl_{2(aq)} + Cl_{2(g)}$
How many grams of $HCl$ react with $5.0\ g$ of manganese dioxide?

$5.75 \ mg$ of sodium vapour is converted to sodium ion. If the ionisation energy of sodium is $490 \ kJ \ mol^{-1}$ and atomic weight is $23 \ g \ mol^{-1}$, the amount of energy needed for this conversion will be (in $kJ$)