Sulphuric Acid Reactions (school) — Conc Named

Remember three roles depending on the reaction: strong acid, dehydrating agent, and oxidizing agent.

Concentrated sulphuric acid has a strong affinity for water and can remove the elements of water from some substances. This is dehydrating action. It can also act as an oxidizing agent in suitable reactions. For example, concentrated sulphuric acid can oxidize copper while itself being reduced to sulphur dioxide: Cu + 2H₂SO₄(conc.) → CuSO₄ + SO₂ + 2H₂O This differs from the simple behaviour of dilute sulphuric acid with reactive metals, which typically gives hydrogen. Do not apply the dilute-acid + metal → H₂ rule blindly to concentrated H₂SO₄.

Concentrated H₂SO₄ does more than simply behave like an acid. It can dry substances (dehydrating) and it can oxidize some metals such as copper, giving SO₂ rather than H₂.

Always check whether a question says dilute or concentrated sulphuric acid. Dilute: typical acid reactions. Concentrated: extra dehydrating and oxidizing chemistry.

Oxidizing behaviour arises from sulphur in a high oxidation state. Dehydrating behaviour is associated with a strong affinity for water. The copper reaction is a standard named example of concentrated-acid oxidation.

Concentrated H₂SO₄: dehydrating + oxidizing (as well as a strong acid).