Question

When chlorine gas is passed through potassium bromide solution, potassium chloride and bromine are formed. Which is a more reactive non-metal: bromine or chlorine? Give reasons for your answer.

Answer 1

Hint: The type of reaction in which part of one reactant is displaced by another reactant is called displacement reaction. In a displacement reaction: a more reactive metal will displace a less reactive metal from its compounds.

Step by step answer: When chlorine \[\left( {C{l_2}} \right)\]gas is passed through potassium bromide \[\left( {KBr} \right)\]solution, potassium chloride \[\left( {KCl} \right)\]and bromine \[\left( {B{r_2}} \right)\]are formed. Which gives orange color to the solution.
\[\]\[2KB{r_{\left( {aq} \right)}} + {\text{ }}C{l_{2\left( {aq} \right)}} \to 2KC{l_{\left( {aq} \right)}} + B{r_{2\left( {aq} \right)}}\]
In this reaction bromine is replaced by chlorine. Chlorine is more reactive than bromine. The order of reactivity is\[Chlorine{\text{ }} > {\text{ }}Bromine\]. It is because the electronegativity of chlorine is more than that of bromine
The above reaction is an example of displacement reaction.

Additional Information: The non-metal elements in Group-7 known as the halogens - get less reactive as we go down the group. This is the opposite trend to that seen in the alkali metals in Group 1 (alkali metals) of the periodic table.
The order of reactivity is\[chlorine{\text{ }} > {\text{ }}bromine{\text{ }} > {\text{ }}iodine\]. This is because chlorine could displace bromine and iodine, bromine could only displace iodine, but iodine could not displace chlorine or bromine. Fluorine is the most reactive among all the halogens.

Note: Students may get confused in deciding the trend of reactivity in groups containing metals ( like alkali metals and alkali earth metals) and the group containing nonmetals ( like halogens). The trend is opposite. In alkali & alkali earth metals reactivity increases down the group while for halogens it decreases.