Describe the characteristic properties of bases in terms of their reactions with: (a) acids (b) ammonium salts

Acids, bases and salts – The characteristic properties of acids and bases

Characteristic properties of bases

Bases are the “opposites” of acids. Think of them as the *cool* side of a chemical reaction – they’re slippery, bitter, and they turn red litmus paper blue. Here’s a quick list of what makes a base a base:

• 🧪 Slippery feel – like a soap solution.
• 😋 Bitter taste – (never taste in real life, just a textbook fact).
• 🔵 Turns red litmus paper blue.
• 💧 Neutralises acids to give water and a salt.
• 🧬 Can be strong (e.g., NaOH) or weak (e.g., NH₃).

Reactions of bases with acids

When a base meets an acid, they “neutralise” each other. The base takes the proton (H⁺) from the acid, forming water, while the remaining ions pair up to make a salt.

1. Base donates a hydroxide ion (OH⁻).
2. Acid donates a proton (H⁺).
3. H⁺ + OH⁻ → H₂O.
4. Remaining cation + anion → salt.

Example:

🔬 Why it matters: This neutralisation reaction is the basis for many everyday processes, like treating acid reflux with antacids.

Reactions of bases with ammonium salts

Ammonium salts (e.g., NH₄Cl) contain the NH₄⁺ ion, which is a weak acid. A strong base will grab the proton from NH₄⁺, releasing ammonia gas (NH₃) and forming water.

1. Base (OH⁻) attacks NH₄⁺.
2. NH₄⁺ loses H⁺ → NH₃ (gas).
3. OH⁻ + H⁺ → H₂O.
4. Remaining cation + anion → new salt.

Example:

💨 Notice the gas: The ammonia that bubbles out is a classic sign that a base has reacted with an ammonium salt.

🔍 Key takeaway: Bases can neutralise acids and also “steal” protons from ammonium salts, producing ammonia gas and a new salt.