Which one of the following statements is NOT correct?
- A.A scale measuring hydrogen ion concentration in a solution is called pH scale
- B.The higher the hydrogen ion concentration in a solution, higher is its pH
- C.We can measure pH generally from 0 to 14 on a pH scale
- D.The 'p' in pH stands for 'potenz' in German meaning power
Correct answer
Explanation
The correct answer is B. pH falls, not rises, as hydrogen ion concentration rises, so a more acidic solution has a lower pH.
pH is defined as the negative logarithm of the hydrogen ion concentration: pH = −log[H⁺]. Because of the minus sign, a larger [H⁺] gives a smaller pH, and each step of one unit means a tenfold change in concentration. At 25°C pure water has pH 7, acids are below 7 and bases above 7. The scale was introduced by the Danish chemist S. P. L. Sørensen in 1909, and the letter p comes from the German word potenz, meaning power.
A is wrong because the pH scale does measure hydrogen ion concentration, so the statement is correct.
C is wrong because pH is generally measured from 0 (very acidic) to 14 (very basic), so the statement is correct.
D is wrong because 'p' does stand for potenz, meaning power, so the statement is correct.
Exam tip: pH = −log[H⁺]; more H⁺, lower pH; one pH unit = ten times the H⁺.
Practice Questions
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1. Alfalfa
2. Amaranth
3. Chickpea
4. Clover
5. Purslane (Kulfa)
6. Spinach
Select the correct answer using the code given below:
- A.1, 3 and 4 only
- B.1, 3, 5 and 6 only
- C.2, 4, 5 and 6 only
- D.1, 2, 4, 5 and 6
Show answer
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- C.Beta and Gamma radiations only
- D.Alpha, Beta and Gamma radiations
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