The molecular formula of aluminium sulphate is

Write the chemical names of the following compounds:
$(a)$ $K_{2}SO_{4}$
$(b)$ $Mg_{3}(PO_{4})_{2}$
$(c)$ $NH_{4}Cl$
$(d)$ $ZnS$
$(e)$ $Na_{3}N$
$(f)$ $AgBr$

Give the chemical formulae for the following compounds and compute the ratio by mass of the combining elements in each one of them:
$(a)$ Ammonia
$(b)$ Carbon monoxide
$(c)$ Hydrogen chloride
$(d)$ Aluminium fluoride
$(e)$ Magnesium sulphide

What is meant by the term chemical formula?

$(a)$ The ratio of hydrogen and oxygen in water is $1:8$ by mass. Find out their ratio by number of atoms in one molecule of water.
(Atomic mass: $H=1 \ u, O=16 \ u)$
$(b)$ Write the formulae of the following compounds:
$(i)$ Ammonium sulphate
$(ii)$ Magnesium chloride
(Given: Ammonium $= NH_{4}^{+}$,Sulphate $= SO_{4}^{2-}$,Magnesium $= Mg^{2+}$,Chloride $= Cl^{-}$)

Give the names of the elements present in the following compounds:
$(a)$ Quick lime
$(b)$ Hydrogen bromide
$(c)$ Baking powder
$(d)$ Potassium sulphate