A compound contains $25\%$ hydrogen and $75\%$ carbon by mass. Determine the empirical formula of the compound.

Calculate the weight of iron that will be converted into its oxide by the action of $18 \mathrm{g}$ of steam.

Unbalanced reaction: $\mathrm{Fe}+{\mathrm{H}}_2\mathrm{O}\stackrel{∆}{⟶}{\mathrm{Fe}}_3{\mathrm{O}}_4+{\mathrm{H}}_2$

A sample of ${\mathrm{KClO}}_3$ on decomposition yields $448 \mathrm{mL}$ of oxygen gas at $\mathrm{NTP}$. Calculate the following:

($\mathrm{i}$) Weight of oxygen product
($\mathrm{ii}$) Weight of ${\mathrm{KClO}}_3$ originally taken and
($\mathrm{iii}$) Weight of $\mathrm{KCl}$ produced.($\mathrm{K}=39, \mathrm{Cl}=35.5$ and $\mathrm{O}=16$)

The percent yield for the following reaction carried out in carbon tetrachloride $\left({\mathrm{CCl}}_4\right)$ solution is $80\%$.

${\mathrm{Br}}_2+{\mathrm{Cl}}_2⟶2\mathrm{BrCl}$

(a) What amount of $\mathrm{BrCl}$ would be formed from the reaction of $0.025 \mathrm{mol} {\mathrm{Br}}_2$ and $0.025 \mathrm{mol} {\mathrm{Cl}}_2$?
(b) What amount of ${\mathrm{Br}}_2$ is left unchanged?

${\mathrm{KCIO}}_3$ decomposes by two parallel reactions,

($i$) $2{\mathrm{KClO}}_3\stackrel{\Delta }{⟶}2\mathrm{KCl}+3{\mathrm{O}}_2$  ($ii$) $4{\mathrm{KClO}}_3\stackrel{\Delta }{⟶}3{\mathrm{KClO}}_4+\mathrm{KCl}$

If $3$ moles of ${\mathrm{O}}_2$ and$1\mathrm{mol}$ of ${\mathrm{KClO}}_4$ is produced along with other products, then determine the initial moles of ${\mathrm{KClO}}_3$.