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NDA 1 2025 GAT, question 78

Topic: Chemistry

Q78

Which one of the following statements is NOT correct?

  1. (a) A scale measuring hydrogen ion concentration in a solution is called pH scale
  2. (b) The higher the hydrogen ion concentration in a solution, higher is its pHCorrect answer
  3. (c) We can measure pH generally from 0 to 14 on a pH scale
  4. (d) The ‘p’ in pH stands for ‘potenz’ in German meaning power

Solution.

Answer: (b) The higher the hydrogen ion concentration in a solution, higher is its pH

  1. At school level, pH=−log⁡10[H+]pH = - \log_{10}\left\lbrack H^{+} \right\rbrack.
  2. Increasing hydrogen-ion concentration therefore decreases pH.
  3. For example, changing [H+]\left\lbrack H^{+} \right\rbrack from 10−310^{- 3} to 10−210^{- 2} changes pH from 3 to 2.
  4. Thus (b) states the relationship backwards.