Question

Take a magnesium ribbon about 3-4 cm long by rubbing it with sand paper.
Hold it with a pair of tongs. Burn it using a sprit lamp or burner and collect
the ash so formed in the watch glass. Dissolve this ash in water and test this
solution with litmus paper. Red litmus paper turns into blue colour.
(a) Why should a magnesium ribbon be cleaned before burning in air?
(b) What flame colour is produced when magnesium burns?
(c) Is magnesium oxidized or reduced in this reaction?
(d) Write chemical reaction for burning of magnesium ribbon?

Answer 1

Explanation:

a)Magnesium ribbon should be cleaned with sandpaper before burning in the air.To remove the Magnesium oxide layer from the ribbon which may prevent or slow down the burning of magnesium ribbon. Unwanted impurities deposited on the magnesium ribbon can be removed and only pure magnesium can be used for the reaction

b)As the magnesium starts to burn, the flame is at first a red-orange, and then turns bright white as the flame reaches its full temperature in the bottom right panel.

c)Magnesium oxidizes and therefore acts as a reducing agent in this reaction.

d)2Mg + O2⟶ 2MgO