Question

When chlorine reacts with sodium bromide the solution turns brown because ____________.
(A) chlorine oxidises bromide
(B) bromine reduces chlorine
(C) both A and B
(D) chlorine displace bromine

Answer 1

Hint: In this question, halogen displacement reaction will take place. Halogens belong to group 7 of the periodic table and down the group reactivity of halogen will decrease. Chlorine is more reactive than bromine.

Complete step by step solution:
From your chemistry lessons, you have learned about the halogen group. In the periodic table, halogens belong to the group no. 7 and as we down the group the reactivity of halogen also decreases.
The reactivity series of halogen is,
F>Cl>Br>I
Reactivity of chlorine is higher than bromine and reactivity of bromine is higher than iodine. Here, we will use the Halogen displacement reaction to solve this question.
Halogen displacement reaction involves a process in which a halogen gains electrons and the halide ion will lose electrons.
In the above reaction when chlorine is added in sodium bromide solution, then the chlorine will take the place of bromine because as we know from the reactivity series that chlorine is more reactive than bromine and thus chlorine will displace the bromine from the sodium bromide solution.
After the displacement reaction, the solution will turn brown in colour. This brown colour is due to the displaced bromine and the chlorine will combine with the sodium to form sodium chloride.
In the above reaction, the changing of position takes place as you can see in the reaction given below,
\[Chlorine+sodium\,bromide\to Sodium\,chloride+bro\min e(brown\,color)\]
\[C{{l}_{2}}(aq)+2NaBr(aq)\to 2NaCl(aq)+B{{r}_{2}}(aq)\]\[\]

Thus the correct option is (D).

Note: Group 17 elements are reactive nonmetals and usually form compounds with other elements. The most reactive halogen is not displaced by any other halogen from a solution of its salts. The meaning of the word halogen is salt former and the displacement reaction is followed by all the halogens.