What Are Salts?
When we think of 'salt', we usually think of the white crystals we sprinkle on food — sodium chloride (NaCl). But in chemistry, salt has a much broader meaning.
A salt is an ionic compound formed when the hydrogen ion (H⁺) from an acid is replaced by a metal ion (or ammonium ion, NH₄⁺). Salts are produced in neutralisation reactions between an acid and a base.
Every salt has two parts:
- The cation (positive ion) — comes from the base (metal hydroxide, metal oxide, metal carbonate, or metal itself)
- The anion (negative ion) — comes from the acid
For example:
- Hydrochloric acid (HCl) produces chloride salts (e.g., sodium chloride, NaCl)
- Sulfuric acid (H₂SO₄) produces sulfate salts (e.g., copper sulfate, CuSO₄)
- Nitric acid (HNO₃) produces nitrate salts (e.g., potassium nitrate, KNO₃)
Think of an acid as a car with a hydrogen 'driver'. In a neutralisation reaction, the hydrogen driver gets out and a metal ion climbs in to take its place — creating a new salt compound.
Naming Salts
Naming salts follows a simple, consistent pattern that you can apply to any acid-base combination.
The name of a salt = name of metal (or ammonium) + name of the acid's anion
The anion name depends on the acid:
| Acid | Anion Name | Example Salt |
|---|---|---|
| Hydrochloric acid (HCl) | chloride | Magnesium chloride (MgCl₂) |
| Sulfuric acid (H₂SO₄) | sulfate | Zinc sulfate (ZnSO₄) |
| Nitric acid (HNO₃) | nitrate | Calcium nitrate (Ca(NO₃)₂) |
| Phosphoric acid (H₃PO₄) | phosphate | Sodium phosphate (Na₃PO₄) |
| Ethanoic acid (CH₃COOH) | ethanoate | Copper ethanoate (Cu(CH₃COO)₂) |
Here's a more reliable naming rule: binary acids (containing only hydrogen and a non-metal, like HCl, HBr, H₂S) give salts ending in -ide (chloride, bromide, sulfide). Oxoacids (containing hydrogen, a non-metal, AND oxygen, like sulfuric, nitric, and nitrous acids) give salts ending in -ate or -ite. Be careful — sulfuric acid ends in '-ic' but gives sulfate salts, NOT sulfide! The key distinction is whether the acid contains oxygen, not just how it ends.
Students often forget that the charge on the salt ions must balance. For example, magnesium (Mg²⁺) with chloride (Cl⁻) needs TWO chloride ions: MgCl₂, not MgCl.
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