(a) Rank ethanol, methylamine, and acetic acid in decreasing order of acidity.
(b) Rank ethanol, methylamine (pKb 3.36), and ethoxide ion (CH3CH2O-) in decreasing order of basicity. In each case, explain your ranking.
Solution 17P :
Acids are chemical agents or substances that release hydrogen ions (H+) into solutions or when added to water. i.e, it is a ion or molecule that donates hydrogen ions or disassociates into hydrogen ions.
The strength of acids are measured using a pH scale. It is a scale that is used to represent the level of acidity in a solution. A solution with a pH of 7 is neutral, and a solution with a pH below 7 is an acid, and a solution with a pH above 7 is a base. A strong acid will have a strong conjugate base after donation of proton. The pKa value and the conjugate base determines the order of acidity.
Ethanol is a weak acid. It also acts as weak base. It is similar to water. Methylamine is a base and acetic acid is an acid.
The pKa value of ethanol is 15.9 . The pKa value of methylamine is 40 and the pKa value of acetic acid is 4.75. Hence acetic acid is strong acid or more acidic and ethanol is less acidic than acetic acid and methylamine is a least acidic.
Hence the decreasing order of acids would be :
Acetic acid > ethanol > methylamine