If the density of iron is $7.86 \, g \, cm^{-3}$ and its atomic mass is $55.85 \, u$,then find the volume occupied by $1 \, mol$ of iron atoms in $cm^{3}$.

The weight of sodium carbonate required to prepare $500 \ mL$ of a semi-normal solution is .......... $g$.

When oxygen is heated in the presence of a catalyst,$15 \%$ of it is converted into ozone. How many grams of oxygen are required to produce $33.6 \, L$ of $O_3$ at $STP$?

If the concentration of $Al^{+3}$ in an aqueous solution of $Al_2(SO_4)_3$ is $1.8 \ M$,what will be the concentration of $SO_4^{-2}$ ions (in $M$)?

$18 \ L$ mixture of $N_2$ and $H_2$ gives maximum $6 \ L$ of $NH_3$ at same temperature and pressure. What will be the ratio of $N_2$ and $H_2$ initially taken?

$100 \, mL$ of $0.1 \, N \, HCl$ is neutralized by $0.2 \, N \, NaOH$ solution. After adding $30 \, mL$ of $NaOH$ solution,the neutralization is continued using $0.25 \, N \, KOH$. Calculate the volume of $KOH$ in $mL$ required to complete the neutralization.