Question

Which type of oxide is obtained when
alkali metals are heated at high
temperature in excess of oxygen ?

Answer 1

Answer:

Lithium tarnishes slowly due to its relatively slow reaction with oxygen.

lithium + oxygen → lithium oxide

4Li(s) + O2(g) → 2Li2O(s)

Sodium

Sodium tarnishes more quickly than lithium, which is further evidence for the greater reactivity of sodium when compared to lithium.

sodium + oxygen → sodium oxide

4Na(s) + O2(g) → 2Na2O(s)

Potassium

Potassium tarnishes so quickly that it is difficult to see that potassium is actually a shiny metal. This is further evidence that potassium is a more reactive metal than both lithium and sodium.

potassium + oxygen → potassium oxide

4K(s) + O2(g) → 2K2O(s)

Explanation:

Combustion

The alkali metals can also be set alight and burn. When any substance burns in oxygen it is called a combustion reaction. Potassium (lilac) burns most vigorously followed by sodium (orange-yellow) and then lithium (red), as you might expect.