The compound that causes water hardness is primarily calcium carbonate (CaCO3) and magnesium carbonate (MgCO3). These minerals can dissolve in water, leading to the formation of hard water. Other compounds, such as calcium sulfate (CaSO4) and magnesium sulfate (MgSO4), can also contribute to water hardness.
Hard water is typically caused by the presence of dissolved minerals, primarily calcium and magnesium ions, in water. These minerals are usually present in the form of calcium carbonate (CaCO3) and magnesium carbonate (MgCO3). Other ions, such as bicarbonates and sulfates, can also contribute to water hardness.
The hardness of water is often categorized into two types:
1. Temporary Hardness:
- Mainly caused by the presence of bicarbonate ions (HCO3-) of calcium and magnesium.
- When water is heated, temporary hardness can be reduced or "precipitated" as the bicarbonate ions convert to insoluble carbonates.
- The chemical reaction involved is:
Ca(HCO3)2 –> CaCO3 + CO2 + H2O
- A similar reaction occurs for magnesium.
2. Permanent Hardness:
- Caused by the presence of sulfates, chlorides, and other non-carbonate salts of calcium and magnesium.
- These ions do not precipitate with heat and require other treatment methods for removal.
The hardness of water can be measured in terms of calcium carbonate equivalents (CaCO3). Water is often classified as soft, moderately hard, hard, or very hard based on the concentration of these minerals. Hard water can have various effects, including the formation of scale in pipes and appliances, reduced soap effectiveness, and potential issues in industrial processes and water heaters. Water softening methods, such as ion exchange or chemical precipitation, are commonly employed to reduce water hardness.