Wednesday, 7 January 2015

4.3.3 - Laboratory Activity : Studying the reaction of alkali metals with halogens

Laboratory Activity 4.3.3:
Studying the reaction of alkali metals with halogens
Aim: To study the reaction of alkali metals with halogens
Problem statement: How do lithium, sodium and potassium differ in reactivity with chlorine gas?
Hypothesis: Reactivity increases for the reaction between alkali metals and chlorine gas when going down Group 1
» Fixed variable : Concentration of chlorine gas
» Manipulated variable : Type of alkali metal
» Responding variable : Reactivity of the metal with chlorine gas

» Lithium
» Sodium
» Potassium
» Filter paper

» Gas jar with cover
» Gas jar spoon
» Small knife
» Test tube
» Forceps
» Bunsen burner

1. The animation below shows the procedures and observation of the experiment.
2. A small piece of lithium is cut with a knife. Dry it with filter paper
3. The lithium is placed in the gas jar spoon by using a forceps.
4. The lithium is heated until it begins to burn, then it is plunged into a gas jar filled with chlorine. All observation are recorded.
5. The experiment is repeated using sodium and potassium.

Metal Observation
Lithium Burns slowly with a red flame. Forms a white solid.
Sodium Burns quickly with a bright yellow flame. Forms a white solid.
Potassium Burns vigorously with a brilliant purple flame. Forms a white solid.

Lithium, sodium and potassium react with chlorine to produce a white metallic chloride.
2Li(s) + Cl2(g) 2LiCl(s)
2Na(s) + Cl2(g) 2NaCl(s)
2K(s) + Cl2(g) 2KCl(s)

All Group 1 metals react with chlorine to form a metallic chloride.

The reactivity increases down the Group 1.

The hypothesis is accepted.

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