## 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
Variable:
 » Fixed variable : Concentration of chlorine gas » Manipulated variable : Type of alkali metal » Responding variable : Reactivity of the metal with chlorine gas

 Material: » Lithium » Sodium » Potassium » Filter paper Apparatus: » Gas jar with cover » Gas jar spoon » Small knife » Test tube » Forceps » Bunsen burner
Procedure:

 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.
Results:

 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.
Discussion:

Lithium, sodium and potassium react with chlorine to produce a white metallic chloride.
 ○ $2Li\left(s\right) +{\mathrm{Cl}}_{2}\left(g\right)\to 2LiCl\left(s\right)$ ○ $2Na\left(s\right) +{\mathrm{Cl}}_{2}\left(g\right)\to 2NaCl\left(s\right)$ ○ $2K\left(s\right) +{\mathrm{Cl}}_{2}\left(g\right)\to 2KCl\left(s\right)$
Conclusion:
 ► All Group 1 metals react with chlorine to form a metallic chloride. ► The reactivity increases down the Group 1. ► The hypothesis is accepted.