In the manufacture of bromine from sea water, the mother liquor containing bromides is treated with:
A. $C{O_2}$
B. $C{l_2}$
C. ${I_2}$
D. $S{O_2}$

Hint: The bromine available for extraction occurs as bromide in the ocean, in salt lakes and in brine or saline deposits left by evaporation of such waters by solar heat. Sea bitterns, the leftover concentrated solution after the crystallizing out of salt from the sea water, are very rich in bromine and offer a good raw material for the manufacture of bromine.

Complete answer:
he manufacturing process of bromine involves four main stages:
(i) Oxidation of bromide ions into bromine.
(ii) Bromine vapour removal.
(iii) Hydrogen bromide production.
(iv) Oxidation of hydrogen bromide to bromine.
We need to determine which substance is used to treat the mother liquor containing bromides in order to get bromine. In the first three steps, the procedure is employed to achieve the mother liquor which contains bromide ions in the combined state. In the last and final step, the oxidation of hydrogen bromide to bromine takes place with the help of chlorine. The reaction that takes place here is:
$C{l_{2(g)}} + 2B{r^ - } \to 2C{l^ - }_{(aq)} + B{r_{2(aq)}}$
The chlorine gas oxidizes the bromide ions to bromine and itself gets reduced to chloride ions. Sea water contains approximately 65,000 tonnes of bromine. This bromine is removed from the sea water by displacement of the bromide ions using chlorine.

Thus, the correct option is B.

Note:
Bromine is used in a variety of ways:
(i) In flame retardants.
(ii) In bromomethane, a chemical used as a fumigant against pests.
(iii) It used to be used as an anti-knock substance with lead, but this has been phased out as lead compounds damage the environment, and catalytic converters.