Hardness of water can be removed by which of the following chemical reagents?

DSSSB - 28 August 2019 (Shift-1)

Non Nursing Subjects

Easy

Appeared in: DSSSB - 28 August 2019 (Shift-1)

Explanation

Sodium carbonate (also known as washing soda or soda ash) is a standard chemical used to remove both temporary and permanent hardness from water.
It operates through a precipitation reaction, converting soluble calcium (Ca²⁺) and magnesium (Mg²⁺) salts into insoluble carbonates (e.g., calcium carbonate, CaCO₃).
Once these minerals precipitate out as solids, they can be removed from the water by filtration or settling, resulting in softened water.

Option A: Magnesium carbonate is one of the very substances that causes water hardness, particularly temporary hardness when it is in its bicarbonate form. It is not used to remove hardness.
Option C: Copper sulphate is primarily used as an algaecide and fungicide in water treatment to control the growth of algae and other microorganisms in reservoirs and pools.
Option D: Sulphur dioxide is used in water treatment, but its main purpose is dechlorination (to remove excess chlorine) or as a reducing agent. It does not remove the mineral ions that cause hardness.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Chemical methods for water softening as background academic context rather than a clinical decision trigger.
In healthcare settings, hard water is problematic as it causes mineral scale buildup in critical equipment like autoclaves and sterilizers. This scale can harbor microorganisms and reduce the effectiveness of sterilization.
Using softened water for hospital laundry is essential. It allows detergents to work efficiently, prevents mineral deposits on fabrics, and helps maintain high standards of hygiene.
What if? If a hospital's central sterile services department (CSSD) uses hard water in its autoclaves, the resulting scale can act as an insulator on heating elements, leading to incomplete sterilization cycles. This poses a significant patient safety risk from potentially unsterile surgical instruments.

How to Approach the Question

First, identify the core concept of the question, which is the 'removal of water hardness'.
Recall or deduce that water hardness is caused by dissolved minerals, specifically calcium and magnesium salts.
Evaluate the options based on their chemical properties. The goal is to find a substance that can remove calcium and magnesium ions from the water.
Recognize that Sodium Carbonate (washing soda) is a common water softener that works by precipitating the hardness-causing minerals.
Eliminate the other options by identifying their primary uses: Magnesium carbonate causes hardness, Copper Sulphate is an algaecide, and Sulphur Dioxide is used for dechlorination.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) p. 44-46