Acids, Bases and Salt Preparation
Acids release H⁺ ions when dissolved in water. The three main ones are hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and nitric acid (HNO₃). They react with metals, metal oxides, hydroxides, and carbonates to form salts.
Bases neutralise acids to form water. Metal hydroxides that dissolve in water are called alkalis and release OH⁻ ions. The pH scale shows how acidic or alkaline something is - below 7 is acidic, above 7 is alkaline, and 7 is neutral.
The general neutralisation reaction is: H⁺(aq) + OH⁻(aq) → H₂O(l). Acids react with carbonates to produce salt, water, and carbon dioxide. With some metals, they produce salt and hydrogen gas instead.
Practical Tip: To make pure salt crystals, react excess base with acid, filter off the excess, then evaporate the water slowly.
For crystallisation practicals, you heat the acid, add excess insoluble base until no more reacts, filter to remove excess, then evaporate the solution slowly to form crystals. This gives you pure salt crystals every time.