The atomic weights of two elements $\mathrm{A}$ and $\mathrm{B}$ are $40$ and $80$, respectively. If $\text{'}\mathrm{x}\text{'} \mathrm{g}$ of $\mathrm{A}$ contains $\mathrm{y}$ atoms, how many atoms are present in $\text{'}2\mathrm{x}\text{'} \mathrm{g}$ of $\mathrm{B}$?

The equation $2\mathrm{Al}\left(\mathrm{s}\right)+\frac{3}{2}{\mathrm{O}}_2\left(\mathrm{g}\right)⟶{\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)$ shows that:

Zinc and hydrochloric acid react according to the reaction:

$\mathrm{Zn}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)⟶{\mathrm{ZnCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

If $0.30 \mathrm{mole}$ of $\mathrm{Zn}$ is added to hydrochloric acid containing $0.52 \mathrm{mole}$ of $\mathrm{HCl}$, how many moles of ${\mathrm{H}}_2$ are produced?

How many moles of Lead $\left(\mathrm{II}\right)$ Chloride will be formed from a reaction between $6.5\mathrm{g}$ of $\mathrm{PbO}$ and $3.2\mathrm{g}$ of $\mathrm{HCl}$

Given the atomic mass of $\left(\mathrm{Pb}=207.2\right)$