Hardness of water is caused by the presence of

Correct option is D

Hardness of water is primarily due to the presence of cations, specifically calcium (Ca²⁺) and magnesium (Mg²⁺) ions. When water flows over or through certain rocks, such as limestone and dolomite, these cations dissolve into the water, contributing to its hardness. There are two main types of hardness: temporary hardness, which can be removed by boiling the water and involves bicarbonates of calcium and magnesium, and permanent hardness, which remains after boiling and is caused by sulfates or chlorides of these cations.
Information Booster Water hardness is classified based on the concentration of calcium and magnesium ions:
1. Soft Water: Contains less than 60 mg/L of calcium carbonate.
2. Moderately Hard Water: Has between 61-120 mg/L of calcium carbonate.
3. Hard Water: Contains between 121-180 mg/L of calcium carbonate.
4. Very Hard Water: Exceeds 180 mg/L of calcium carbonate.
Hardness in water affects household and industrial applications. For instance, it can cause scale formation in pipes and appliances, reducing their efficiency and lifespan. Softening processes, such as ion exchange or chemical precipitation, are often applied to reduce hardness, making water suitable for various uses, including washing and cooking.
Additional Knowledge · Solid Particles in Water (Option A): Solid particles or suspended solids in water can include silt, clay, and organic matter. While they affect the turbidity and appearance of water, they do not cause hardness.
· Pathogens in Water (Option B): Pathogens are microorganisms, such as bacteria, viruses, and protozoa, that can cause diseases. Their presence indicates biological contamination but does not influence water hardness.
· Toxic Metals in Water (Option C): Toxic metals, such as lead, arsenic, and mercury, may pollute water and pose significant health risks. However, they do not contribute to water hardness as they do not have the same effect on scaling as calcium and magnesium ions.