Chapter 20: Chlorine and hypochlorite

All the following "answers" are for your reference only!

The "best" answers are based on your actual experimental results!

 

Experiment 20.1: Making and testing bleach in the laboratory

2.   Bubbles of gas.

3.   Hydrogen ions are discharged at the cathode.

2H⁺(aq) + 2e^- ¾® H₂(g)

4.   Chloride ions are discharged at the anode.

2Cl^-(aq) ¾® Cl₂(g) + 2e^-

5.   A swimming pool smell / smell of chlorine / smell of bleach.

6.   The pH appear turns blue then white.

7.   The colour fades.

8.   The stain fades.

9.   Cl₂(g) + 2NaOH(aq) ¾® NaOCl(aq) + NaCl(aq) + H₂O(l)

10. As hydrogen ions are discharged at the cathode, hydroxide ions are left behind.

At the anode, chloride ions are discharged leaving sodium ions behind.

The remaining solution contains sodium hydroxide.

 

Experiment 20.2: Action of acid on chlorine bleach

3.   It turns red and then bleaches to colourless.

4.   Green / yellow.

5.   Chlorine.

6.   Cl₂(g) + H₂O(l)

 

Experiment 20.3: Action of chlorine water on halide solutions

1.   Colourless.

Orange / yellow

The colourless bromide changes to bromine which is orange in colour.

2Br^-(aq) ¾® Br₂(g) + 2e^-

2.   Colourless.

Brown / yellow.

The colourless iodide ion changes to iodine.

2I^-(aq) ¾® I₂(aq)/(s) + 2e^-

(The black solid is due to the formation of iodine solid.)

3.   In both cases, bromide and iodide are oxidized by chlorine.