Reactivity of Alkali Metal with Chlorine, Oxygen and Water

 Reaction with Chlorine

1. All alkali metals react with chlorine gas to form white metal chlorides salt.

 Group 1 Metals (2X) + Chlorine Gas (Cl2)→ 

  Metal Chloride (2XCl)

2.The metal chlorides salt formed is soluble in water to give a neutral solution of pH 7.

3.The reactivity increases down the group from 

a) lithium -burned slowly with a reddish flame . A white solid is                 produced.

b) sodium -burned brightly with a yellowish flame. A white solid is produced

c) potassium- burned very brightly with a purplish flame . A white solid is produced.

Reaction with Oxygen

1. Group 1 metals react with oxygen gas produces metal oxides. These metal oxides dissolve in water produces alkali.
Group 1 Metals (4X) + Oxygen Gas (O2)→
 Metal Oxide(2X2O)
2. Lithium, sodium and potassium form white oxide powders after reacting with oxygen.
3. The white powder is the oxide of lithium, sodium and potassium.
4. When the white powder is dissolved in water, it produces a solution which turned red litmus paper blue. Which means, these oxides dissolve in water to form strong alkali.
5. The reactivity increases down the group from 

a) lithium-burns with red flame and produces white powder immediately after reaction.

b) sodium -burned with bright yellow flame, forming white powder immediately after                          reaction.

c) potassium- burned with very bright purplish flame, forming white powder immediately                        after reaction.

Reaction with Water

Group 1 metals react vigorously with water produces alkali and hydrogen gas

Group 1 Metals + Water → Alkali + Hydrogen gas

2X + 2H2O --> 2XOH + H2 (where X is alkali metal)

Common Observation

1. Lithium, sodium or potassium floats and move around on the surface of the water and then dissolve in the water.
Conclusion: Lithium, sodium and potassium are less dense than water.
2. Colourless gas is released around the metal. The gas produces a “pop” sound when ignited with lighted wooden splinter.
Conclusion: The colourless flammable gas is hydrogen.
3. The solution turn blue when it is tested with universal indicator.
Conclusion: the solution produced is an alkali.
4. The reactivity increases down the group from

a) Lithium - moves slowly on the surface of water with 'fizzing' sound.

b) Sodium - moves swiftly on the surface of water with 'fizzing' sound.

c) Potassium - reacts violently with water, move very fast on the surface of water and           burn with lilac flame.

Solubility of the Oxide Hydroxide and Salt of Alkali Metals

1. All the oxide and hydroxide of group 1 metal are soluble in water to form an alkali solution.
2. All the salts (salt of chloride, nitrate, sulphate, carbonate....) of group 1 metals are soluble in water. The solutions formed are neutral.