Question

The ash which is collected after burning of magnesium ribbon is dissolved in water to give a solution X. What is the nature of the solution X when it is tested with indicators?
A) It turns blue litmus red and phenolphthalein pink, hence it is an acidic solution.
B) It turns red litmus blue and phenolphthalein pink, hence it is a basic solution.
C) It turns blue litmus red and gives no colour with phenolphthalein, hence it is an acidic solution.
D) It does not change the colour of red or blue litmus and phenolphthalein, hence it is a neutral solution.

Answer 1

Hint: We know that when magnesium ribbon is burned, the ash that is formed is magnesium oxide. Magnesium oxide is basic oxide. We must know the product of the reaction of basic oxide and water.

Complete step-by-step answer:
We know that when magnesium ribbon is burned in air the ash formed is magnesium oxide. The oxides that react with water to form a base or oxides that react with an acid to form a salt are known as basic oxides. Magnesium oxide is a basic oxide. Thus, magnesium oxide being a basic oxide reacts with water and forms a base.Thus, the solution X is a basic solution.

We know that the basic solutions turn blue litmus red. Also, we know that the colour of phenolphthalein is pink in basic solutions.Thus, solution X turns phenolphthalein pink. Thus, the solution X turns red litmus blue and phenolphthalein pink. Thus, the solution X turns red litmus blue and phenolphthalein pink, hence it is a basic solution.

Thus, the correct option is option (B) it turns red litmus blue and phenolphthalein pink, hence it is a basic solution.

Note: The acidic solutions turn blue litmus red and give no colour with phenolphthalein. The basic solutions turn red litmus blue and give pink colour with phenolphthalein. And the neutral solutions do not change the colour of red or blue litmus and phenolphthalein. Hus, the red and blue litmus and phenolphthalein are known as the indicators. These indicators help in identifying the acidic or basic or neutral nature of the solution.