The pH of a weak mono basic acid is 5. The degree of ionisation of acid in 0.1 M solution is

PH of weak monobasic acid is 55=12PKa-logC0⇒10=PKa+1⇒PKa=9⇒Ka=10-9degree of ionisaiton of a weak acid is given asα=KaC0=10-910-1=10-4 or H+=Cα ; α=10-510-1=10-4;