Question

Sodium hydroxide in water gives
A. yellow colour solution
B. green colour solution
C. colourless solution
D. light pink solution

Answer 1

To answer this question we should alkali metal halides. The sodium hydroxide is an alkali metal hydroxide. It is also known as caustic soda. It is a white solid at room temperature. It is used as a drain cleaner.

Complete answer:
The chemical formula of sodium hydroxide is NaOH. The sodium is an alkali metal and the group –OH is known as hydroxide. The sodium hydroxide gives the hydroxide ion so, sodium hydroxide is a base.
Sodium hydroxide is an ionic compound. The ionic compound dissociates into ions in water. The base sodium hydroxide on dissolving in water dissociates into a sodium ion and chloride ions.
The reaction of dissolution is shown as follows:
${\text{NaOH}}\,\mathop { \to \,}\limits^{{{\text{H}}_2}{\text{O}}} {\text{N}}{{\text{a}}^{\text{ + }}}{\text{(aq)}}\,\,\,{\text{ + }}\,\,{\text{O}}{{\text{H}}^ - }{\text{(aq)}}$
Sodium hydroxide itself is a colourless solid so, on dissolving in water its ions do not give any colour to the solution.
So, the sodium hydroxide in water gives a colourless solution.
Therefore, option (C) colourless solution is correct.

Note: The alkali metal hydroxide is prepared by dissolving the alkali metal in water. The hydrogen gas evolved during this reaction. The reaction of an alkali metal with water is very vigorous. The alkali metal hydroxide is colourless but they form crystals that appear white in colour. Alkali metal hydroxides are soluble in water and are base. The sodium hydroxide is used in saponification. It is also used in the chlor alkali process for the production of sodium hydroxide. Sodium hydroxide is a strong base, so it is used as a cleansing agent as it is corrosive.