Hardness of water can be removed by adding

RRB Staff Nurse Ahmedabad-2015

General Knowledge

Easy

Appeared in: RRB Staff Nurse Ahmedabad-2015

Explanation

Water hardness is caused by dissolved calcium and magnesium ions.
The ion-exchange process is a common method to remove these ions, thus softening the water.
In this process, hard water passes through a resin that exchanges calcium/magnesium ions for sodium ions.
Sodium chloride (common salt) is used in a concentrated brine solution to regenerate these resin beads, flushing out the hardness minerals and allowing the system to continue working.
Therefore, among the given options, sodium chloride is the chemical added to the system to facilitate the removal of hardness.

Option A: Calcium chloride is one of the primary mineral salts that causes permanent water hardness.
Option B: Magnesium chloride is another main contributor to permanent water hardness.
Option D: Potassium permanganate is a powerful oxidizing agent used for disinfection and removing iron/manganese from water, not for softening.

Visual 1: Diagram: An infographic illustrating the ion-exchange process in a water softener, showing Ca²⁺/Mg²⁺ ions being trapped by the resin and Na⁺ ions being released. A separate panel should show the regeneration cycle where NaCl is used to flush the trapped minerals.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Water treatment and removal of water hardness as background academic context rather than a clinical decision trigger.
Understanding water quality is a key aspect of community health nursing. Hard water is not a direct health hazard, but it has economic and practical implications for households and healthcare facilities (e.g., scale buildup in sterilizers).
Some studies have suggested a possible inverse relationship between water hardness and cardiovascular disease, meaning areas with harder water might have slightly lower rates of these diseases, though the evidence is not conclusive.
What if a community has very soft water? While good for appliances, very soft water can be corrosive to metal pipes (like lead and copper), potentially leaching these metals into the drinking water, which is a significant health risk. Public health nurses should be aware of the water quality in their service areas.

How to Approach the Question

First, identify the core concept of the question: 'removing water hardness'.
Recall or deduce what causes water hardness. The presence of calcium and magnesium salts is the primary cause.
Analyze each option. Options A (Calcium Chloride) and B (Magnesium Chloride) are the very substances that cause hardness, so they can be eliminated immediately.
Now you are left with Sodium Chloride and Potassium Permanganate. Consider their roles in water treatment.
Recall that Potassium Permanganate is a disinfectant (often used for wells, giving water a pink tint). It doesn't affect hardness.
This leaves Sodium Chloride. Think about how it might be used. It's the salt used in water softener units. Even if you don't add it directly to the drinking water, it's essential for the process of removing hardness. Therefore, it's the most plausible answer.

Concept Tested & Keywords

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