Hydrogen and oxygen combine in the ratio of $1:8$ by mass to form water. What mass of oxygen gas would be required to react completely with $3 \,g$ of hydrogen gas (in $,g$)?

Calculate the molecular masses of $H_2$,$O_2$ and $Cl_2$.

$A$ $0.24 \, g$ sample of a compound of oxygen and boron was found by analysis to contain $0.096 \, g$ of boron and $0.144 \, g$ of oxygen. Calculate the percentage composition of the compound by weight.

Write the chemical formulae of the following:
$(i)$ Magnesium chloride
$(ii)$ Calcium oxide
$(iii)$ Copper nitrate
$(iv)$ Aluminium chloride
$(v)$ Calcium carbonate.

Define the atomic mass unit.

Write down the names of compounds represented by the following formulae:
$(i) Al_{2}(SO_{4})_{3}$
$(ii) CaCl_{2}$
$(iii) K_{2}SO_{4}$
$(iv) KNO_{3}$
$(v) CaCO_{3}$