Calcium reacts with sulphuric acid to produce calcium sulphate and hydrogen gas, but this reaction is quickly inhibited.
Here's a breakdown:
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Initial Reaction: Calcium metal (Ca) reacts with sulphuric acid (H₂SO₄) in a typical acid-metal reaction, producing calcium sulphate (CaSO₄) and hydrogen gas (H₂):
Ca(s) + H₂SO₄(aq) → CaSO₄(s) + H₂(g) -
Formation of a Protective Layer: The key aspect of this reaction is that calcium sulphate (CaSO₄) is only sparingly soluble in water. As calcium sulphate forms, it precipitates out of the solution and coats the surface of the calcium metal.
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Inhibition of Further Reaction: This calcium sulphate coating acts as a barrier, preventing further contact between the sulphuric acid and the remaining calcium metal. Consequently, the reaction quickly slows down and effectively stops. This passivation occurs because the insoluble layer physically blocks the acid from reaching the calcium.
Summary: The reaction between calcium and sulphuric acid is self-limiting due to the formation of an insoluble calcium sulphate layer that prevents further reaction.
