Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
The standard calculation
19 practice questions
Practice questions
1–8 of 8 · Normal
Question 1
2 marks · Normal
Answer and see the solution →A student titrates 25.0 cm³ of potassium hydroxide solution of unknown concentration with 0.150 mol/dm³ hydrochloric acid. The average volume of acid required to neutralise the alkali is 18.0 cm³. Calculate the number of moles of hydrochloric acid ( ) used in the reaction.
Question 2
4 marks · Normal
Answer and see the solution →Ethanoic acid ( ) reacts with sodium hydroxide ( ) according to the equation:
A student titrates 25.0 cm³ of 0.200 mol/dm³ sodium hydroxide with ethanoic acid. On average, 21.0 cm³ of ethanoic acid is needed to neutralise the alkali.
(a)[1 mark]State the ratio in which sodium hydroxide reacts with ethanoic acid.
(b)[1 mark]Calculate the number of moles of sodium hydroxide present in 25.0 cm³.
(c)[1 mark]Calculate the number of moles of ethanoic acid used in the reaction.
(d)[1 mark]Calculate the concentration of the ethanoic acid.
Question 3
3 marks · Normal
Answer and see the solution →In a titration, 25.0 cm³ of sulphuric acid ( ) of unknown concentration is neutralised by 32.5 cm³ of 0.150 mol/dm³ potassium hydroxide ( ). The balanced chemical equation is:
Calculate the concentration of the sulphuric acid.
Question 4
4 marks · Normal
Answer and see the solution →A table shows the results from a titration between lithium hydroxide ( ) and hydrochloric acid ( ).
Titration Results Volume of LiOH (cm³) Concentration of LiOH (mol/dm³) Volume of HCl (cm³) Concentration of HCl (mol/dm³) 25.0 0.100 20.0 ? (a)[1 mark]Write the balanced chemical equation for this reaction.
(b)[1 mark]Calculate the number of moles of LiOH used.
(c)[1 mark]Using the chemical equation, state the number of moles of HCl that reacted.
(d)[1 mark]Calculate the concentration of the HCl solution.
Question 5
1 mark · Normal
Answer and check →Which step should you do first to solve for the unknown concentration in a standard titration calculation?
- A.Calculate the number of moles of the standard solution used
- B.Write the ionic equation for the reaction
- C.Multiply the concentrations of both solutions together
- D.Estimate the endpoint by eye only
Question 6
2 marks · Normal
Answer and see the solution →During a titration experiment, 22.5 cm³ of 0.250 mol/dm³ potassium hydroxide completely neutralises 27.0 cm³ of a sulfuric acid solution. Calculate the number of moles of potassium hydroxide used in the reaction.
Question 7
4 marks · Normal
Answer and see the solution →A sample of nitric acid ( ) reacts with sodium carbonate ( ) solution. The balanced equation is:
A student titrates 25.0 cm³ of 0.150 mol/dm³ sodium carbonate. On average, 36.0 cm³ of nitric acid is required to completely react.
(a)[1 mark]According to the equation, what is the ratio of moles of nitric acid to moles of sodium carbonate required?
(b)[1 mark]Calculate the number of moles of sodium carbonate used.
(c)[1 mark]Determine the number of moles of nitric acid required to react completely.
(d)[1 mark]Calculate the concentration of nitric acid in mol/dm³.
Question 8
3 marks · Normal
Answer and see the solution →A student carries out a titration to find the concentration of a sulfuric acid solution. She adds exactly 25.0 cm³ of sodium hydroxide solution of known concentration, 0.150 mol/dm³, to a conical flask. She slowly adds sulfuric acid from a burette, using methyl orange as an indicator, until the indicator just changes colour. She records that she has used 30.0 cm³ of sulfuric acid to reach the endpoint. The balanced chemical equation for the reaction is:
Explain carefully how you would use these results to calculate the concentration of the sulfuric acid.