Halogens: The Displacers
See how chlorine kicks out bromine and iodine.
What this lesson covers
Why it matters
Bubbling green chlorine gas into a clear liquid triggers a sudden colour change. The solution turns orange-brown as bromine is liberated.
The idea in plain words
Analyze the swap: Chlorine takes the place of Bromine. Check the equation: 2NaBr + Cl₂ → 2NaCl + Br₂.
Predict first
Why does chlorine displace bromine from sodium bromide?
In Group 17, reactivity decreases down the group. Chlorine, being higher up, is more reactive and kicks bromine out.
- Chlorine is more reactive than bromine — correct
- Chlorine is a gas while bromine is a liquid
- Chlorine is heavier than bromine
- Chlorine repels bromine atoms
What you do
First, bubble chlorine into sodium bromide. Note the orange-brown colour. Then, try chlorine with potassium iodide. Observe the brown colour of iodine.
Check yourself
What is the observation when chlorine gas is passed through potassium iodide solution?
The reaction 2KI + Cl₂ → 2KCl + I₂ produces iodine, which turns the solution brown.
Which statement correctly describes the reactivity trend in Group 17?
Chlorine displaces bromine and iodine, proving it is more reactive. Thus, reactivity decreases down the group.
In the reaction 2NaBr + Cl₂ → 2NaCl + Br₂, what is the role of chlorine?
Chlorine is more reactive than bromine, so it displaces bromine from its salt solution.
- Solution turns brown — correct
- Solution turns orange-brown
- No visible change
- Solution turns blue-black
- Reactivity increases down the group
- Reactivity decreases down the group — correct
- Reactivity is constant
- Reactivity depends on atomic mass only
- It acts as a catalyst
- It displaces bromine — correct
- It neutralizes sodium
- It oxidizes sodium