Human body works in the pH range of :
- A.6.8 - 7.2
- B.7.0 - 7.8
- C.6.5 - 7.5
- D.7.5 - 8.0
Correct answer
Explanation
The correct answer is B, 7.0 - 7.8. NCERT's Class 10 chemistry chapter on acids, bases and salts states that our body works within the narrow pH range of 7.0 to 7.8, which is slightly basic. Living organisms can survive only in a small range of pH because enzymes and other proteins lose their shape and stop working when the pH shifts too far. Blood, for example, is held close to pH 7.4 by buffers such as the bicarbonate system; a fall below this range is acidosis and a rise above it is alkalosis. Individual parts of the body differ: the stomach is strongly acidic, around pH 1.5 to 3.5, because of hydrochloric acid, while the small intestine is alkaline. Option A is wrong because 6.8 to 7.2 dips into the acidic side and is not the range NCERT gives. Option C is wrong because 6.5 to 7.5 is too acidic at its lower end. Option D is wrong because 7.5 to 8.0 is too basic and leaves out neutral pH 7. Exam tip: body pH 7.0–7.8; blood ≈ 7.4; stomach acid ≈ 1.5–3.5; tooth decay below 5.5.
Practice Questions
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