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Q124 (IAS/2000) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Applied everyday chemistry Answer Verified

Consider the following statements : Hard water is not suitable for I. drinking. II. washing cloths with soap. III. use in boilers. IV. irrigating crops. Which of these statements are correct ?

Result
Your answer: —  ·  Correct: B
Explanation

II and III are correct. Hard water reacts with Ca2+/Mg2+ to form insoluble “soap scum,” preventing proper lathering and wasting soap, so it is unsuitable for washing clothes with ordinary soap [2]. Hardness ions also precipitate as scale in boilers, reducing heat transfer, efficiency and equipment life, making hard water unsuitable for boiler use [1]. By contrast, dissolved calcium and magnesium in hard water are not inherently harmful for human consumption and can be beneficial in moderation, so “not suitable for drinking” is not universally true. Agricultural guidance treats multiple water-quality parameters (pH, salinity) when assessing irrigation suitability, and hardness alone is not categorically listed as universally unsuitable for all crops and soils [3].

Sources

  1. [1] https://www.stannescet.ac.in/cms/staff/qbank/CSE/Notes/CY8151-Engineering%20Chemistry-1098045625-unit_1%20(1).pdf
  2. [2] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > Activity 4.12 > p. 76
  3. [3] https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0013/164101/Farm-water-quality-and-treatment.pdf
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