4.4.3 - Laboratory Activity : Studying the reaction of halogens with aqueous sodium hydroxide solution.

Laboratory Activity 4.4.3: Studying the reaction of halogens with aqueous sodium hydroxide solution.

Aim: To study the reaction between halogen and sodium hydroxide solution.
Problem statement: How do chlorine, bromine and iodine react with sodium hydroxide solution?
Hypothesis: Reactivity decreases for the reaction between halogen and sodium hydroxide solution when going down Group 17.
Variable:

	»	Fixed variable : sodium hydroxide solution
	»	Manipulated variable : Type of halogen
	»	Responding variable : Reactivity of reaction

Material: » Chlorine gas » Bromine solution » Iodine crystals » Sodium hydroxide solution

Apparatus: » Rubber stopper » Test tube

Procedure:

	►	The animation below shows the procedures and observation of the experiment.
	►	(A) With chlorine 1. Chlorine gas is into a test tube containing sodium hydroxide solution. 2. All observation are recorded.
	►	(B) With bromine 1. The bromine liquid in the boiling tube is warmed up and the vapours are passed through hot iron wool. 2. The test tube is closed with a cork and shake well. 3. All observation are recorded.
	►	(C) With iodine 1. A small iodine crystal is added to a test tube containing sodium hydroxide solution. 2. The test tube is closed with a cork and shake well. 3. All observation are recorded.

Results:

►

Halogen Observation Chlorine Dissolves quickly. Greenish yellow colour of chlorine changes to colourless. Bromine Dissolves less quickly. Forms colourless solution. Iodine Dissolves slowly to form colourless solution.

Discussion:

	►	Chlorine, bromine and iodine react with sodium hydroxide to form sodium halide, sodium hypohalite and water.
	►	Chlorine dissolves quickly in sodium hydroxide solution to produce sodium chloride solution, sodium hypochlorite and water. ○ ${\mathrm{Cl}}_2\mathrm{(g)\; +\; 2NaOH}\to \mathrm{NaCl(aq)\; +\; NaClO(aq)\; +}{H}_2\mathrm{O(l)}$
	►	Bromine dissolves less quickly in sodium hydroxide solution to produce sodium bromide solution, sodium hypobromite and water. ○ ${\mathrm{Br}}_2\mathrm{(g)\; +\; 2NaOH}\to \mathrm{NaBr(aq)\; +\; NaBrO(aq)\; +}{H}_2\mathrm{O(l)}$
	►	Iodine dissolves slowly in sodium hydroxide solution to produce sodium iodide solution, sodium hypoiodite and water. ○ ${\mathrm{I}}_2\mathrm{(g)\; +\; 2NaOH}\to \mathrm{NaI(aq)\; +\; NaIO(aq)\; +}{H}_2\mathrm{O(l)}$
	►	The reactivity of the halogens with sodium hydroxide solution decreases when going down Group 17.

Conclusion:

	►	Halogens react with sodium hydroxide solution.
	►	The reactivity increases down the Group 17.
	►	The hypothesis is accepted.

↶ 4.4 Group 17 Elements

⇲ For exercise(objective and subjective), download for free on Android OS.