Question

When magnesium is burned in air, a powdery ash X is formed. X on dissolving in water forms Y.
i. What are X and Y.
ii. What is the action of Y on litmus paper?
iii. What conclusion do you get about the nature of Y from its action on litmus paper?
iv. What is the common name of the indigestion-relieving medicine which contains Y?

Answer 1

i) The X is magnesium oxide and the Y is magnesium hydroxide.

• When the magnesium burns into air, an oxidation reaction takes place and the atmospheric oxygen combines with the magnesium in order to form magnesium oxide. (Magnesium oxide is powdery)

2Mg + O2 ---> 2MgO

• Now,when the magnesium oxide reacts with water,it forms magnesium hydroxide.

MgO + H2O ----> Mg(OH)2

ii) The Y or magnesium hydroxide turns the red litmus paper into blue litmus paper.

iii) The Y or magnesium hydroxide is a basic substance because it turns red litmus into blue litmus.

iv) The Y or magnesium hydroxide containing medicine for indigestion,is known as the milk of magnesia.