A piece of paper is burnt in air, the gas produced is passed through distilled water, the pH of water will be
Correct answer: C. 6.8
- A. 7
- B. 3
- C. 6.8
- D. 2.1
Explanation
When paper, which is composed of organic material, is burnt, carbon dioxide (CO2) is produced. When CO2 is passed through distilled water, it reacts to form carbonic acid (H2CO3), a weak acid. This reaction slightly lowers the pH of the water from 7 to around 6.8, making Option C the correct choice. Option A is incorrect because it assumes no change in pH, which does not account for the acidic nature of carbonic acid. Option B assumes a stronger acidity than what carbonic acid would produce, and Option D indicates a very strong acid, which is not the case here.
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About Acids, Bases and Salts
Acid and base behaviour is explained through the Bronsted-Lowry transfer of protons and the Lewis donation or acceptance of electron pairs. The topic includes pH, pOH, ionisation and water equilibrium, plus salt formation and hydrolysis, where a salt solution may become acidic, basic or neutral.
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