In which of the following gas mixtures does Dalton's Law of Partial Pressure not apply? Why?
$(i)$ $CO_2 + O_2 + N_2$
$(ii)$ $CO + O_2$
$(iii)$ $NH_3 + HCl$
$(iv)$ $HCl + O_2$

(B, C) Dalton's Law of Partial Pressure applies only to non-reacting gas mixtures.
$(i)$ $CO_2 + O_2 + N_2$ and $(iv)$ $HCl + O_2$ are non-reacting mixtures,so the law applies.
$(ii)$ $CO + O_2$ and $(iii)$ $NH_3 + HCl$ are reacting mixtures,so the law does not apply.
Chemical reactions:
$(ii)$ $2CO + O_2 \rightarrow 2CO_2$
$(iii)$ $NH_3 + HCl \rightarrow NH_4Cl$