Acid–alkali indicators
3 marks · EasyThe table shows five solutions and their pH values.
| Solution | pH |
|---|---|
| P | 3 |
| Q | 6 |
| R | 7 |
| S | 9 |
| T | 13 |
Identify which solution is neutral.
State which solution is a weak acid.
Which solution is strongly alkaline? Explain your answer.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) R
(b) Q
(c) T. It is strongly alkaline because it has a pH of 13, which is within the strongly alkaline range (11–14).
Common mistakes: Mixing up weak and strong acid/alkali
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Identifies R as the neutral solution (pH 7).
B2 (b) · 1 mark · Identifies Q as weak acid (pH 6).
M1 (c) · 1 mark · Identifies T as strongly alkaline and gives a correct reason (pH 13 is 11–14 range).
Worked solution
a. R is neutral because it has pH 7. b. Q is a weak acid because pH 4–6 is weakly acidic. c. T is strongly alkaline because it has pH 13, which fits the strongly alkaline range (pH 11–14).