A farmer finds that the soil has a pH of 5. Which substance should be added to the soil to raise its pH for better crop growth?
Answer and explanation
Correct answer: Quicklime (CaO)
The pH scale shows that a pH below 7 represents an acidic substance; therefore, soil with pH 5 is acidic. Quicklime, CaO, is a basic oxide. In moist soil it forms calcium hydroxide, which neutralises excess acidity and raises the pH toward a more suitable range. HCl would increase acidity, while ammonium chloride is an acidic salt and sodium chloride is not the appropriate corrective material. Option A is correct.
Frequently asked questions
What is the correct answer to this question?
Quicklime (CaO)
Why is this the correct answer?
The pH scale shows that a pH below 7 represents an acidic substance; therefore, soil with pH 5 is acidic. Quicklime, CaO, is a basic oxide. In moist soil it forms calcium hydroxide, which neutralises excess acidity and raises the pH toward a more suitable range. HCl would increase acidity, while ammonium chloride is an acidic salt and sodium chloride is not the appropriate corrective material. Option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
