The following data are obtained when dinitrogen and dioxygen react together to form different compounds:

Mass of dinitrogen	Mass of dioxygen
$(i) \ 14 \ g$	$16 \ g$
$(ii) \ 14 \ g$	$32 \ g$
$(iii) \ 28 \ g$	$32 \ g$
$(iv) \ 28 \ g$	$80 \ g$

$(a)$ Which law of chemical combination is obeyed by the above experimental data? Give its statement.
$(b)$ Fill in the blanks in the following conversions:
$(i) \ 1 \ km = \dots \ mm = \dots \ pm$
$(ii) \ 1 \ mg = \dots \ kg = \dots \ ng$
$(iii) \ 1 \ mL = \dots \ L = \dots \ dm^{3}$

(N/A) If we fix the mass of dinitrogen at $28 \ g$, the masses of dioxygen that combine with the fixed mass of dinitrogen are $32 \ g, 64 \ g, 32 \ g,$ and $80 \ g$.
The ratio of these masses of dioxygen is $32:64:32:80$, which simplifies to $2:4:2:5$ (a whole number ratio).
Thus, the data obeys the Law of Multiple Proportions.
Statement: When two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in the ratio of small whole numbers.
$(b) (i) \ 1 \ km = 10^{6} \ mm = 10^{15} \ pm$
$(ii) \ 1 \ mg = 10^{-6} \ kg = 10^{6} \ ng$
$(iii) \ 1 \ mL = 10^{-3} \ L = 10^{-3} \ dm^{3}$