Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Acids, Alkalis and Titrations
83 practice questions
Topics covered
Practice questions
71–80 of 83
Question 71
4 marks · Normal
Answer and see the solution →The steps below are used in a titration experiment to find the volume of sulfuric acid needed to neutralise 25.0 cm³ of potassium hydroxide solution.
(a)[1 mark]State how the potassium hydroxide solution should be measured and transferred to the flask.
(b)[2 marks]Name a suitable indicator for this titration, and state the expected colour change at the endpoint.
(c)[1 mark]Explain why it is important to read the burette at eye level.
Question 72
2 marks · Normal
Answer and see the solution →Describe two key steps you would take to accurately find the volume of sulfuric acid needed to neutralise a fixed amount of sodium hydroxide solution using a titration. Do not include any calculation steps.
Question 73
2 marks · Hard
Answer and see the solution →State two steps you must carry out before starting to add alkali from a burette in a titration experiment between hydrochloric acid and sodium hydroxide. Do not include steps taken during or after the addition of alkali.
Question 74
5 marks · Hard
Answer and see the solution →A student is asked to carry out an acid-alkali titration to determine the volume of sulfuric acid needed to neutralise 25.0 cm³ of sodium hydroxide solution.
(a)[2 marks]Describe, in order, four steps the student should take to set up the experiment before beginning the titration.
(b)[2 marks]Explain why phenolphthalein is a suitable indicator for this titration, and why universal indicator should not be used.
(c)[1 mark]State how the student would recognise the endpoint of the titration.
Question 75
2 marks · Hard
Answer and see the solution →During a titration, a student adds hydrochloric acid to sodium hydroxide solution from a burette. The student does a 'rough titration' first, then repeats the procedure more carefully. Explain the purpose of doing a rough titration, and describe one way to increase accuracy when repeating the titration.
Question 76
5 marks · Easy
Answer and see the solution →Vinegar and household ammonia are tested using two different indicators:
(a)[1 mark]State which solution is acidic and which is alkaline.
(b)[1 mark]A drop of vinegar is placed on blue litmus paper. Describe what is observed.
(c)[2 marks]Household ammonia is tested with universal indicator. Name the colour you would expect and explain what this indicates about its pH.
(d)[1 mark]Explain how universal indicator is used to measure the pH of a solution.
Question 77
5 marks · Easy
Answer and see the solution →The table below shows the colours of three indicators in different solutions.
Indicator results for solutions A, B and C. Solution Litmus Phenolphthalein Methyl orange A Red Colourless Red B Blue Pink Yellow C Purple Colourless Yellow (a)[3 marks]Using the table, state which solution is acidic, which is alkaline, and which is neutral. Explain your answers using indicator colours.
(b)[2 marks]For solution B, state what the pH is likely to be, and justify your answer.
Question 78
5 marks · Easy
Answer and see the solution →Two solutions, X and Y, are tested:
Test results with universal indicator and methyl orange. Solution Universal indicator colour Methyl orange colour X Orange Red Y Blue Yellow (a)[2 marks]Estimate the pH value for each solution from the universal indicator colour. Show your reasoning.
(b)[2 marks]Classify each solution as strongly acidic, weakly acidic, neutral, weakly alkaline, or strongly alkaline based on your estimated pH values.
(c)[1 mark]Referring to the methyl orange results, explain whether your classifications are supported. Give reasons for your answer.
Question 79
5 marks · Easy
Answer and see the solution →A student tests a sample of rainwater using universal indicator paper. The paper turns yellow-green.
(a)[2 marks]What does the colour yellow-green indicate about the pH of the rainwater? Estimate the pH value.
(b)[1 mark]Is the rainwater acidic, neutral or alkaline? Explain your answer.
(c)[2 marks]Describe how you would use universal indicator solution, rather than paper, to measure the pH of rainwater.
Question 80
6 marks · Normal
Answer and see the solution →A student investigates different alkaline solutions and later performs a titration.
(a)[1 mark]State the ion responsible for the alkalinity of sodium carbonate solution.
(b)[2 marks]Write the ionic equation for how carbonate ions in sodium carbonate solution produce this ion, using water.
(c)[1 mark]The student uses sodium carbonate solution in a titration with hydrochloric acid. Name the piece of apparatus they should use to measure 25.0 cm³ of sodium carbonate solution accurately into a conical flask.
(d)[2 marks]State the indicator that should be used for this titration and give the colour change expected at the endpoint.