Overview
The action of metals when exposed to acids and bases is a classic chapter in chemical reactivity. Such reactions are fundamental in both laboratory and real-world settings (such as corrosion, production of salts, and hydrogen gas evolution). The character of the reaction depends on the reactivity of the metal and whether it interacts with an acid or a base.
Metal Reactions with Acids
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Most metals react with acids to produce a salt and hydrogen gas.
- General reaction: Metal + Acid → Salt + Hydrogen gas
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Example:
Zinc reacts with hydrochloric acid:
Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)↑
- Not all metals react equally: Noble metals like gold and platinum do not react with dilute acids.
Metal Reactions with Bases
- Most metals do not react with bases. However, a few, especially amphoteric metals like zinc and aluminium, do.
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Amphoteric Metals:
Metals that react with both acids and bases.
Zn(s) + 2NaOH(aq) + 2H₂O(l) → Na₂[Zn(OH)₄](aq) + H₂(g)↑
This type of reaction is less common than acid-metal reactions and produces complex ions (e.g., [Zn(OH)₄]²⁻) along with hydrogen gas.
Key Points & Safety
- Reaction vigor depends on metal reactivity (see Activity Series chart).
- Hydrogen gas evolved in these reactions is flammable—handle with care.
- Some metals (e.g., sodium, potassium) react explosively with acids and bases; laboratory protocols require caution.
Simple Activity Series of Metals
Credit: LibreTexts (Source)