A 0.1 M aqueous solution of a monoprotic weak acid HA is found to be isotonic with a 0.12 M aqueous solution of urea at the same temperature. The percentage degree of dissociation of the weak acid HA is.

Step-by-step solution

For isotonic solutions at the same temperature, their osmotic pressures are equal: _ HA = _ urea Using the formula = iCRT : i_ HA C_ HA RT = i_ urea C_ urea RT Since urea is a non-electrolyte, i_ urea = 1 . i_ HA 0.1 = 1 0.12 i_ HA = 1.2 For the dissociation of a monoprotic weak acid HA : HA H ^+ + A ^- The number of ions produced per molecule, n = 2 . The van't Hoff factor i is related to the degree of dissociation by: i = 1 + (n - 1) 1.2 = 1 + (2 - 1) = 0.2 The percentage degree of dissociation is: % = 0.2 100 =