Q3
1 markMCQSection A

The body of human beings works within the pH range of:

Acids, Bases and Salts
pH range of human body

Options

(A)6-1 to 6-8
(B)6-5 to 7-3
(C)7-0 to 7-8
(D)7-5 to 8-1
Official Answer

(C) 7.0 to 7.8

Quick Oral Answer

The human body functions within a narrow pH range of 7.0 to 7.8; deviations outside this narrow window disrupt enzyme activity and metabolic processes.

Analysis & Explanation

Section 2.3.1 of the chapter states directly: 'Our body works within the pH range of 7.0 to 7.8. Living organisms can survive only in a narrow range of pH change.'


  • (C) 7.0 to 7.8 — correct. This is the exact range stated in the NCERT textbook for the human body's optimal metabolic pH.
  • (A) 6.1 to 6.8 — incorrect. This range is too acidic and too low; it does not correspond to any value given in the chapter for the human body's working pH.
  • (B) 6.5 to 7.3 — incorrect. Though close to neutral, this range does not match the textbook's stated value and dips below the physiological range needed for enzymes and metabolic activities to function properly.
  • (D) 7.5 to 8.1 — incorrect. This range is shifted too high (too alkaline) compared to the textbook value of 7.0 to 7.8.

Common Mistakes

  1. 1Confusing the human body's pH range (7.0–7.8) with the neutral pH value of pure water (pH 7).
  2. 2Misremembering the exact bounds and shifting the range too high or too low.

Interesting Facts

When the pH of rain water falls below 5.6, it is termed acid rain, and it can disturb the pH balance of rivers and harm aquatic life.

Tooth decay begins when the pH inside the mouth drops below 5.5, since it corrodes the calcium hydroxyapatite of tooth enamel.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2025?

This question carries 1 mark in the CBSE Class 10 Science 2025 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Acids, Bases and Salts" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "pH range of human body" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2025 paper?

This is a MCQ question from Section A in the CBSE Class 10 Science 2025 paper.