How to deduce Nature of Salt in Salt Hydrolysis |
Posted: November 18, 2018 |
A salt can be acidic, neutral or alkaline. We can deduce the nature of the salt from its constituent ions, namely: 1. ion formed from a weak acid will be a conjugate base, eg CH3COO- (from weak acid CH3COOH) 2. ion formed from a strong acid will be neutral, eg Cl- (from strong acid HCl) 3. ion formed from a weak base will be a conjugate acid, eg NH4+ (from weak base NH3) 4. ion formed from a strong base will be neutral, eg Na+ (from strong base NaOH) This can be summarised as shown: salt hydrolysis nature of ions summary Next we can move on to deduce the nature of a salt. Let's have some examples. 1. Sodium chloride NaCl is neutral salt hydrolysis sodium chloride neutral Na+ is neutral since it is formed from strong base NaOH Cl- is neutral since it is formed from strong acid HCl Since both cation and anion are neutral, NaCl must be neutral. 2. Sodium ethanoate CH3COONa is alkaline Na+ is neutral since it is formed from strong base NaOH. CH3COO- is alkaline since it is the conjugate base of weak acid CH3COOH. Since we have a conjugate base, CH3COO- will dissociate in water to give OH-, hence the salt is alkaline. 3. Ammonium chloride NH4Cl is acidic Cl- is neutral since it is formed from strong acid HCl. NH4+ is acidic since it is the conjugate acid of weak base NH3. Since we have a conjugate acid, NH4+ will dissociate in water to give H+, hence the salt is acidic. Watch this video to learn an easy way to understand salt hydrolysis, a concept that students often find confusing in Ionic Equilibria! Topic: Ionic Equilibria, Physical Chemistry, A Level Chemistry, Singapore You can also view this video lesson with screenshots and detailed explanation. Do check out the following for more video lessons: If you are looking for H2 Chemistry Tuition, do consider taking up my classes at Bishan. You can also find out more about my online classes
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