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Displacement equations of the halogens
You should have found that chlorine was the most reactive of the three halogens that you studied, so it displaced the other two halogens. Bromine is the next most reactive, so it displaced the iodine but not the chlorine. The following equations show the reactions which took place, no reaction occurred for the others:
| Cl2(aq) + 2KI(aq) ⇒ I2(aq) + 2KCl(aq)- | or Cl2(aq) + 2I-(aq) ⇒ I2(aq) + 2Cl-(aq) |
| Cl2(aq) + 2KBr(aq) ⇒ Br2(aq) + 2KCl(aq)- | or Cl2(aq) + 2Br-(aq) ⇒ Br2(aq) + 2Cl-(aq) |
| Br2(aq) + 2KI(aq) ⇒ I2(aq) + 2KBr(aq)- | or Br2(aq) + 2I-(aq) ⇒ I2(aq) + 2Br-(aq) |
The solutions should have turned brown where iodine was produced. In the reaction which produced bromine a yellow-orange colour is seen. If the iodine and bromine solutions are dilute they both look yellow and can be difficult to tell apart. This is where the hydrocarbon solvent test comes in useful.