Acid–alkali indicators
2 marks · EasyA universal indicator chart is shown below.
| pH | Colour |
|---|---|
| 2 | red |
| 5 | orange |
| 7 | green |
| 10 | blue |
| 13 | purple |
A student tests a solution and sees that it turns orange with universal indicator.
(a)[1 mark]
Estimate the pH of the solution based on the chart.
(b)[1 mark]
Classify the solution as strongly acidic, weakly acidic, neutral, weakly alkaline, or strongly alkaline.
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) 5
(b) Weakly acidic
Common mistakes: Misclassifying an orange solution as neutral
Show mark scheme and worked solution
Marking points
A1 (a) · 1 mark · Estimates pH as about 5 (accept 4–6).
B1 (b) · 1 mark · Classifies solution as weakly acidic.
Worked solution
a. Orange on the chart is at pH 5. b. pH 5 is in the range 4–6, so the solution is weakly acidic.