Ncert Exercises & Solutions

Arrange the following compounds in decreasing order of acidity.
H,0, ROH, HC==CH

A stronger acid displaces a weaker acid from its salt. When RONa is treated with

H_{2} O

, it forms ROH. So, water is a stronger acid than ROH.

HOH +RONa $\to$ NaOH + ROH

Stronger acid Weaker acid

Similarly, when sodium ethynide is treated with water and alcohol, then acetylene is obtained.
HOH + CH $\equiv$ CNa $\to$ HC $\equiv$ CH+ NaOH

Stronger acid Weak acid

ROH + HC $\equiv$ CNa $\to$ HC $\equiv$ CH + RONa
Stronger acid Weak acid

Thus, water and alcohol are stronger acid than ethyne and the decreasing order of acidity of given compounds are

HOH > ROH > HC $\equiv$ CH