Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
pH and indicators
19 practice questions
Practice questions
1–3 of 3 · Hard
Question 1
2 marks · Hard
Answer and see the solution →State the colours that phenolphthalein and methyl orange turn in a strongly alkaline solution.
Question 2
5 marks · Hard
Answer and see the solution →An unknown solution is tested with universal indicator. The indicator turns blue-green and the estimated pH is 8.
(a)[2 marks]Use the pH scale to classify the solution as strongly acidic, weakly acidic, neutral, weakly alkaline, or strongly alkaline. Give a reason for your answer.
(b)[1 mark]State what the pH value tells you about the concentration of hydrogen ions compared to a solution of pH 7.
(c)[2 marks]Describe how you would use universal indicator to estimate the pH of an aqueous solution. Include what you would observe and what you would compare it to.
Question 3
2 marks · Hard
Answer and see the solution →Explain how adding an acid to an alkaline solution changes its pH. State what happens to the indicator colour if universal indicator is used throughout.