Temporary hardness of water can be removed by?

Appeared in: RRB Staff Nurse Mumbai-2015

Explanation

Temporary hardness is caused by soluble bicarbonates of calcium and magnesium.
Boiling decomposes these thermally unstable bicarbonates into insoluble precipitates (calcium carbonate and magnesium hydroxide).
These precipitates can then be easily removed by filtration or decantation, thus softening the water.
This method is effective for temporary (carbonate) hardness but not for permanent (non-carbonate) hardness.

Option A: Calcium chloride is a salt that causes permanent hardness in water.
Option B: Magnesium chloride, similar to calcium chloride, is a cause of permanent hardness in water.
Option C: Sodium chloride (common salt) does not remove water hardness directly.

Visual 1: Diagram - A simple diagram showing a beaker of hard water being boiled, with arrows indicating the precipitation of calcium carbonate and magnesium hydroxide at the bottom.
Visual 2: Flowchart - A flowchart distinguishing between temporary and permanent hardness, listing their causes and respective removal methods side-by-side for easy comparison.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Water Hardness and Removal Methods as background academic context rather than a clinical decision trigger.
In a hospital setting, hard water can cause scaling (a hard, chalky deposit) inside autoclaves, water heaters, and boilers. This reduces efficiency, increases energy costs, and can damage expensive equipment.
Hard water requires more soap and detergent to form a lather, impacting cleaning and hand hygiene protocols. Using softened water can improve cleaning effectiveness and reduce supply costs.
What if the water had permanent hardness? If the water hardness was due to calcium and magnesium sulfates (permanent hardness), boiling would have no effect. In that case, methods like ion exchange or adding washing soda would be required for softening.

How to Approach the Question

First, identify the key term in the question: 'Temporary hardness'.
Recall the definition of temporary hardness – it's caused by soluble bicarbonates of calcium and magnesium.
Remember that these bicarbonates are unstable when heated.
Evaluate the options based on this knowledge. 'Boiling' is a direct method of heating.
Eliminate the other options by recalling that chlorides and sulfates cause 'permanent hardness', and sodium chloride is used for regenerating softeners, not for direct softening.

Concept Tested & Keywords

QuMt4iy27vIXGqCu39lELB

Practise the full RRB Staff Nurse Mumbai-2015

Attempt every question from this paper in a timed mock, then review the full solution for each one.