Nitrogen atom has an atomic number of $7$ and oxygen has an atomic number of $8$. The total number of electrons in a nitrate ion $(NO_3^-)$ will be:

$3.0$ molal $NaOH$ solution has a density of $1.110 \, g/mL$. The molarity of the solution is

If one liter of air is repeatedly passed over heated copper and magnesium until no further reduction in volume occurs,the final volume of the air will be approximately ......... $mL$.

If $1 \ g$ of each of the following gases are taken at $STP$,which of the gases will occupy $(a)$ greatest volume and $(b)$ smallest volume? $CO, H_2O, CH_4, NO$

When $1 \ L$ of $N/5 \ HCl$ aqueous solution in a beaker is boiled,the volume of the resulting solution becomes $250 \ mL$. During this process,$3.65 \ g$ of $HCl$ is lost. What will be the concentration of the resulting solution? $(HCl = 36.5 \ g/mol)$

$200 \ mL$ of a mixture of $50\% \ H_2$,$40\% \ CH_4$ and $10\% \ CO_2$ is exploded with excess of oxygen in an eudiometry tube. The resultant mixture is cooled to room temperature and is passed through $aq. KOH$. Find volume contraction after passing through $KOH$ ................. $mL$