pH and indicators
4 marks · NormalThe table below shows the pH values of four different aqueous solutions.
| Solution | pH |
|---|---|
| P | 2 |
| Q | 5 |
| R | 8 |
| S | 13 |
State which solution is strongly acidic.
State which solution is neutral.
State which solution is weakly alkaline.
State which solution is strongly alkaline.
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(a) P
(b) Q (None)
(c) R
(d) S
Common mistakes: Mixing up strongly/weakly acidic and alkaline ranges
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Marking points
B1 (a) · 1 mark · Correctly identifies P as strongly acidic (pH 2).
B1 (b) · 1 mark · Correctly identifies none as neutral (no pH=7). Accepts Q if they explain pH 5 is closest to neutral.
B1 (c) · 1 mark · Correctly identifies R as weakly alkaline (pH 8).
B1 (d) · 1 mark · Correctly identifies S as strongly alkaline (pH 13).
Worked solution
a) Strongly acidic: pH 0–3, so P (pH 2).
b) Neutral: pH 7. None of the solutions have pH 7.
c) Weakly alkaline: pH 8–10, so R (pH 8).
d) Strongly alkaline: pH 11–14, so S (pH 13).