$2$:The percentage composi$$on of a sample of coal by weight was

found to be C $=72\%,$ H $=6\mathrm{.}5\%,$ O $=13\%,$ N $=2\mathrm{.}5\%,$ S $=1\mathrm{.}8\%$

i$)$ Calculate the minimum weight of air for complete combus$$on

ii$)$ Calculate the weight of dry products formed if $50$ percent excess air