JAMB - Chemistry (2024 - No. 29)
The ions responsible for permanent hardness in water are sulphates of
Fe\(^{3+}\) and Mg\(^{2+}\)
Ca\(^{2+}\) and Mg\(^{2+}\)
Fe\(^{2+}\) and Fe\(^{3+}\)
Na\(^{+}\) and Ca\(^{2+}\)
Spiegazione
Water is considered permanently hard when it contains soluble chlorides and sulphates of calcium and magnesium. These salts do not precipitate out when the temperature increases, so boiling the water will not remove them.