Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
pH and indicators
19 practice questions
Practice questions
11–19 of 19
Question 11
3 marks · Normal
Answer and see the solution →A student adds methyl orange to a solution. The solution turns yellow. They mix the solution with just enough acid to make the colour just change to red.
Estimate the change in pH that the student has achieved. State your reasoning.
Question 12
3 marks · Normal
Answer and see the solution →Explain why a solution with pH 6 is described as weakly acidic and how you could confirm this using an indicator.
Question 13
4 marks · Normal
Answer and see the solution →The table shows the effect of three indicators in different solutions.
Solution Litmus Methyl orange Phenolphthalein Vinegar red red colourless Soapy water blue yellow pink (a)[2 marks]State which solution is acidic. Explain your answer using the indicator results.
(b)[2 marks]State which solution is alkaline. Explain your answer using the indicator results.
Question 14
1 mark · Normal
Answer and check →Which pH value shows a strongly alkaline solution?
- A.pH 2
- B.pH 6
- C.pH 9
- D.pH 13
Question 15
2 marks · Normal
Answer and see the solution →Name two indicators that can distinguish between an acid and an alkali, and state the colour each shows in an alkali.
Question 16
4 marks · Normal
Answer and see the solution →A teacher gives three solutions: X with pH 3, Y with pH 7, and Z with pH 12.
(a)[3 marks]Classify each solution as acidic, neutral, or alkaline.
(b)[1 mark]State which solution is strongly acidic and which is strongly alkaline.
Question 17
2 marks · Hard
Answer and see the solution →State the colours that phenolphthalein and methyl orange turn in a strongly alkaline solution.
Question 18
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 19
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.