Name of the solution | Colour change with phenolphthalein | Colour change with blue litmus |
(a) Sodium carbonate | ||
(b) Hydrochloric acid | ||
(c) Sodium chloride |
Answer:
Basic solutions turn red litmus paper blue.
The salt of a weak acid and a strong base gives a basic solution. So, the given
salt X is the salt of a weak acid and strong base.
Example:
When sodium carbonate is dissolved in water, it gets hydrolyzed to some extent
and forms sodium hydroxide and carbonic acid.
Being
a strong base, sodium hydroxide is fully ionized and gives a large an hydroxide
ions (OH-). Carbonic acid is a weak acid which is only slightly and
hence, gives a small amount of hydrogen ions (H+). The H+
ions prod carbonic acid neutralizes only a small amount of OH" ions
produced by hydroxide and the rest amount of OH- ions are present in
the solution. He Na2CO3 solution is basic in nature. It
turns red litmus blue.
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