Question

Both anionic and cationic hydrolysis occur in the case of (a) salts of strong acid and strong base (b) salts of strong acid and weak base (c) salts of weak acid and strong base (d) salts of weak acid and weak base

Short answer

Both anionic and cationic hydrolysis occurs in the case of salts of weak acid and weak base (option d).

Step-by-step solution

Understand Hydrolysis

Hydrolysis is a reaction involving water that splits an ion or molecule. In context of acids and bases, when a salt (formed from an acid and a base) dissolves in water, it may dissociate into its constituent ions and react with water molecules. This reaction with water is called hydrolysis.

Hydrolysis of Salts of Strong Acid and Strong Base

Salts formed from a strong acid and a strong base do not undergo hydrolysis. This is because both the cation and the anion are unable to react with water molecules.

Hydrolysis of Salts of Strong Acid and Weak Base

Salts of a strong acid and weak base will undergo cationic hydrolysis. This is due to the weak basicity of the cation. In this case, the cation reacts with water to produce the weak base and a hydronium ion.

Hydrolysis of Salts of Weak Acid and Strong Base

In the case of compounds composed of a weak acid and strong base, anionic hydrolysis occurs. Here, the anion from the weak acid reacts with water to produce the weak acid and a hydroxide ion.

Hydrolysis of Salts of Weak Acid and Weak Base

For salts of a weak acid and weak base, both anionic and cationic hydrolysis can occur. The anion reacts with water to form the weak acid and a hydroxide ion, while the cation reacts to form the weak base and a hydronium ion.

Key concepts

Anionic and Cationic Hydrolysis

When you add salt to water, you might expect it to simply dissolve, but there's more to the story. This dissolving process can lead to a reaction known as hydrolysis. Salts arising from strong acids and bases are like well-mannered guests at a party—they don't cause any trouble and just make the water a bit salty. But when weak acids or bases are involved, things get interesting.

Imagine the salt is a button that splits into two parts once it hits the water: one part from an acid, the other from a base. If the acid was weak to start with, the 'acid part' can make the water more basic. Conversely, if the base was a bit hesitant (weak), the 'base part' can turn the water acidic. That's anionic and cationic hydrolysis. Sometimes both can happen at once, but with strong acids and bases, it's like they don't know how to react—so they don't.

Strong Acid and Strong Base

Let's talk about salts made from the tough guys of chemistry: a strong acid and a strong base. Think of hydrogen chloride (HCl) teaming up with sodium hydroxide (NaOH)—when they become a salt, sodium chloride (NaCl), they're pretty stable. Why? Because they've already reacted as much as they want to. When NaCl joins water, there's no hydrolysis because both the Na and Cl are content with where they are—they don't interact with the water. So, in this heavyweight match, no extra acidity or basicity is added, and the water's pH stays neutral.

Strong Acid and Weak Base

When a powerful acid shakes hands with a not-so-strong base and they form a salt, things get a bit off-balance. For instance, if HCl (strong acid) makes a salt with NH₃ (weak base), you get NH₄Cl. The NH₄ part is the weakling here, and in water, it grabs a hydrogen from H₂O, leaving behind OH^- ions and making the water more acidic. This is cationic hydrolysis. The NH₄⁺ ions just feel more at home as weak base NH₃ and H₃O⁺, the hydronium ion. The net result? The pH of the solution tilts towards the acidic side, all thanks to the weak base in the game.

Weak Acid and Strong Base

Flip the situation, and now you've got a weak acid and a strong base. Take acetic acid (CH₃COOH), which isn't so keen on giving up its protons, and pair it with NaOH, a base that's all in. You get a salt like sodium acetate (CH₃COONa). Once it's in water, the sodium part is just fine, but the acetate (CH₃COO^-) wants to react, snatching a hydrogen from water and creating hydroxide ions (OH^-). This is anionic hydrolysis at work, where the 'acid part' of our salt makes the water less acidic, more basic. The water goes from being just plain old water to a bit of a soapy feel—that's the higher pH caused by the excess OH^- ions.

Weak Acid and Weak Base

Now we're entering the territory where everyone's on the fence: salts from a weak acid and a weak base. They're like a pair of indecisive folks who come together to make a salt, but once they're in water, they can't decide if they should go back to being an acid or a base. Because they're both weak, they both end up reacting with the water. That cation might pick up a hydrogen, while the anion drops one off, leading to a hydrolysis dance. The result is a solution where you've got both H₃O⁺ and OH^- floating around, which can slightly affect the pH, often fluctuating around neutral. Imagine this like a tug-of-war where both teams are equally matched – the rope might wiggle a lot, but it doesn't move much in either direction. The pH stays neutral, but the potential for action is there.