Laboratory Activity 1D (Displacement of a Halogen from Its Halide Solution):
Aim: To investigate the redox reaction in the displacement of a halogen from its halide solution.
Materials: Chlorine water, Cl2, bromine water, Br2, iodine, I2 solution, 0.5 mol dm−3 of potassium chloride, KCl solution, 0.5 mol dm−3 of potassium bromide, KBr solution, 0.5 mol dm−3 of potassium iodide, KI solution and organic solvent 1,1,1-trichloroethane, CH3CCl3.
Apparatus: Test tubes, measuring cylinder and test tube rack.
Procedure:
A. The colour of a halogen in the aqueous solution and organic solvent 1,1,1-trichloroethane, CH3CCl3
1. Pour 2 cm3 of chlorine water, Cl2 into a test tube.
2. Add 2 cm3 of the organic solvent 1,1,1-trichloroethane,CH3CCl3 into the test tube as shown in Figure 1.12.
3. Shake the mixture vigorously and leave the test tube for 30 seconds at the test tube rack.
4. Observe and record the colour of the aqueous layer and the layer of 1,1,1-trichloroethane, CH3CCl3.
5. Repeat steps 1 to 4 using bromine water, Br2 and iodine, I2 solution.
B. The displacement reaction of a halogen from its halide solution
1. Pour 2 cm3 of potassium chloride, KCl solution into a test tube.
2. Add 2 cm3 of bromine water, Br2 into the test tube.
3. Shake the mixture and observe any colour change.
4. Add 2 cm3 of 1,1,1-trichloroethane, CH3CCl3, into the test tube.
5. Shake the mixture vigorously and leave the test tube for 30 seconds.
6. Observe and record the colour of the aqueous layer and the layer of 1,1,1-trichloroethane, CH3CCl3.
7. Repeat steps 1 to 6 by using halide solutions and halogens as shown in the following table:
Result:
Construct a suitable table to record all observations in section A and section B.
Answer:
Result:
Table to record all observations.
1. To verify the presence of halogen.
2.
(a) No
(b) Chlorine water.
(c) Chlorine water and bromine water.
3.
KBr and Cl2
(a)
Oxidation half equation : 2Br− → Br2 + 2e−
Reduction half equation : Cl2 + 2e− → 2Cl−
(b) Overall ionic equation : 2Br− + Cl2 → Br2 + 2Cl−
(c)
– Br− ions are oxidised because Br− ions lose electrons to form bromine, Br2 molecules, while chlorine is reduced because chlorine, Cl2 molecules gain electrons to form Cl− ions.
– Chlorine water is an oxidising agent because chlorine is the electron acceptor, while potassium bromide is a reducing agent because Br− ions are the electron donors.
KI and Cl2
(a)
Oxidation half equation : 2I− → I2 + 2e−
Reduction half equation : Cl2 + 2e− → 2Cl−
(b) Overall ionic equation : 2I− + Cl2 → I2 + 2Cl−
(c)
– I− ions are oxidised because. I− ions lose electrons to form iodine, I2 molecules, while chlorine is reduced because chlorine, Cl2 molecules gain electrons to form chloride, Cl− ions.
– Chlorine water is an oxidising agent because chlorine is the electron acceptor, while potassium iodide is a reducing agent because I− ions are the electron donors.
KI and Br2
(a)
Oxidation half equation : 2I− → I2 + 2e−
Reduction half equation : Br2 + 2e− → 2Br−
(b) Overall ionic equation : 2I− + Br2 → I2 + 2Br−
(c)
– I− ions are oxidised because I− ions lose electrons to form iodine, I2 molecules, while bromine is reduced because bromine, Br2 molecules gain electrons to form bromide, Br− ions.
– Bromine water is an oxidising agent because bromine is the electron acceptor, while potassium iodide is a reducing agent because I− ions are the electron donors.
4.
(a) I2, Br2, Cl2
(b) The strength of a halogen as an oxidising agent decreases down Group 17.
(c) Cl−, Br−, I−
Aim: To investigate the redox reaction in the displacement of a halogen from its halide solution.
Materials: Chlorine water, Cl2, bromine water, Br2, iodine, I2 solution, 0.5 mol dm−3 of potassium chloride, KCl solution, 0.5 mol dm−3 of potassium bromide, KBr solution, 0.5 mol dm−3 of potassium iodide, KI solution and organic solvent 1,1,1-trichloroethane, CH3CCl3.
Apparatus: Test tubes, measuring cylinder and test tube rack.
Procedure:
A. The colour of a halogen in the aqueous solution and organic solvent 1,1,1-trichloroethane, CH3CCl3
1. Pour 2 cm3 of chlorine water, Cl2 into a test tube.
2. Add 2 cm3 of the organic solvent 1,1,1-trichloroethane,CH3CCl3 into the test tube as shown in Figure 1.12.
3. Shake the mixture vigorously and leave the test tube for 30 seconds at the test tube rack.
4. Observe and record the colour of the aqueous layer and the layer of 1,1,1-trichloroethane, CH3CCl3.
5. Repeat steps 1 to 4 using bromine water, Br2 and iodine, I2 solution.
B. The displacement reaction of a halogen from its halide solution
1. Pour 2 cm3 of potassium chloride, KCl solution into a test tube.
2. Add 2 cm3 of bromine water, Br2 into the test tube.
3. Shake the mixture and observe any colour change.
4. Add 2 cm3 of 1,1,1-trichloroethane, CH3CCl3, into the test tube.
5. Shake the mixture vigorously and leave the test tube for 30 seconds.
6. Observe and record the colour of the aqueous layer and the layer of 1,1,1-trichloroethane, CH3CCl3.
7. Repeat steps 1 to 6 by using halide solutions and halogens as shown in the following table:
Result:Construct a suitable table to record all observations in section A and section B.
Answer:
Result:
Table to record all observations.
1. To verify the presence of halogen.
2.
(a) No
(b) Chlorine water.
(c) Chlorine water and bromine water.
3.
KBr and Cl2
(a)
Oxidation half equation : 2Br− → Br2 + 2e−
Reduction half equation : Cl2 + 2e− → 2Cl−
(b) Overall ionic equation : 2Br− + Cl2 → Br2 + 2Cl−
(c)
– Br− ions are oxidised because Br− ions lose electrons to form bromine, Br2 molecules, while chlorine is reduced because chlorine, Cl2 molecules gain electrons to form Cl− ions.
– Chlorine water is an oxidising agent because chlorine is the electron acceptor, while potassium bromide is a reducing agent because Br− ions are the electron donors.
KI and Cl2
(a)
Oxidation half equation : 2I− → I2 + 2e−
Reduction half equation : Cl2 + 2e− → 2Cl−
(b) Overall ionic equation : 2I− + Cl2 → I2 + 2Cl−
(c)
– I− ions are oxidised because. I− ions lose electrons to form iodine, I2 molecules, while chlorine is reduced because chlorine, Cl2 molecules gain electrons to form chloride, Cl− ions.
– Chlorine water is an oxidising agent because chlorine is the electron acceptor, while potassium iodide is a reducing agent because I− ions are the electron donors.
KI and Br2
(a)
Oxidation half equation : 2I− → I2 + 2e−
Reduction half equation : Br2 + 2e− → 2Br−
(b) Overall ionic equation : 2I− + Br2 → I2 + 2Br−
(c)
– I− ions are oxidised because I− ions lose electrons to form iodine, I2 molecules, while bromine is reduced because bromine, Br2 molecules gain electrons to form bromide, Br− ions.
– Bromine water is an oxidising agent because bromine is the electron acceptor, while potassium iodide is a reducing agent because I− ions are the electron donors.
4.
(a) I2, Br2, Cl2
(b) The strength of a halogen as an oxidising agent decreases down Group 17.
(c) Cl−, Br−, I−