$($a$)$ Legislation in Hong Kong specifies the sulphur emission standard from coal$-$fired power

stations as follows: $(1)$ the maximum allowable sulphur content in the coal used is $1\%($by

dry weight$)$; $(2)90\%$ of the potential sulphur emission from burning such coal must be

removed.

$($i$)$ For every kilogram of coal burned, what is the maximum allowable sulphur emission $($in

kilograms$)?$

$(2$ marks$)$

$($ii$)$ If we use a throwaway limestone $(CaC{O}_3)$ wet scrubbing system for sulphur removal,

how much limestone $($in kilograms$)$ is required for every kilogram of coal burned?

$(5$ marks$)$

Assume the stoichiometric relation:

$S{O}_2+CaC{O}_3+0\mathrm{.}5H_{2}O*CaS{O}_3*0\mathrm{.}5H_{2}O+C{O}_2$

Atomic masses: S $(32),$ O $(16),$ Ca $(40),$ C $(12),$ H $(1)$

$($iii$)$ What is$($are$)$ the main objection$($s$)$ to using a wet scrubber for removing sulphur?

$(3$ marks$)$