The amount of bleaching powder needed to purify 1000 liter of water is-

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2022

Explanation

The standard recommended dose for routine disinfection of water is 2.5 grams of good quality bleaching powder per 1000 liters.
This dosage provides an approximate applied chlorine concentration of 0.7 mg per litre.
The primary goal is to achieve a free residual chlorine level of at least 0.5 mg/L after a contact time of one hour to ensure the water is safe and protected from re-contamination.

Option A: A dose of 1.5 grams is generally insufficient to meet the chlorine demand of the water and leave an adequate protective residual chlorine level.
Option C: A dose of 5 grams is excessive for routine water purification and would result in an unpalatable taste and odor due to high chlorine levels.
Option D: A dose of 7.5 grams is a very high concentration for drinking water and is not used for routine purification.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Disinfection of water using bleaching powder as background academic context rather than a clinical decision trigger.
Correct chlorination is a fundamental public health measure to prevent major waterborne diseases such as cholera, typhoid, dysentery, and gastroenteritis.
Community health nurses play a crucial role in educating communities on safe water practices, especially in rural areas or during emergencies like floods, where the regular water supply may be compromised.
What if? If the water is visibly turbid or muddy, its chlorine demand will be higher. In this case, more than 2.5 grams of bleaching powder would be needed. It is also recommended to first filter the water through cloth to remove particulate matter, as chlorine is less effective in turbid water.

How to Approach the Question

First, identify the core of the question: it's asking for a standard measurement for a public health procedure (water purification).
Recognize this as a factual recall question based on established community medicine guidelines.
Recall the standard dose of bleaching powder for disinfecting 1000 liters of water.
The standard recommended amount is 2.5 grams.
Evaluate the given options based on this knowledge. 1.5g is too little (ineffective), while 5g and 7.5g are too much (over-chlorination) for routine use.
Select the option that matches the standard dose, which is 2.5gm.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) pp. 34-36, 33-35

Practise the full RUHS, Jaipur, PB B.Sc Nursing Entrance-2022

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