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Aims
Aims
To calculate the percentage of iron in an iron tablet
To calculate the percentage of iron in an iron tablet
To perform a redox titration involving Fe2+(aq) and MnO4 – (aq)
To perform a redox titration involving Fe2+(aq) and MnO4 – (aq)
A. Report & Analyse of Results
A. Report & Analyse of Results
Record your results in an appropriate way
Use concordant results to calculate the average titre and then answer the questions below to calculate the mass of iron in the tablet.
Things to consider CPAC 4b
Things to consider CPAC 4b
CPAC 4b - Obtains accurate, precise and sufficient data for experimental and investigative procedures and records this methodically using appropriate units and conventions.
· Write down the exact burette value to 0.05cm3
· Measure masses to at least 2dp’s (check zeros are included as necessary)
· Obtain 2-3 concordant results
· Data recorded includes units
· Average of concordant results used in calculations
B. Evaluate your report by answering the questions
B. Evaluate your report by answering the questions
1. Combine the two half-equations given below to write the equation for the reaction: Fe2+(aq) → Fe3+ + e− MnO4 − (aq) + 8H+ (aq) + 5e− → Mn2+(aq) + 4H2O(l)
2. Use your average titre to calculate the number of moles of manganate(VII) ions that were used in the titration.
3. Use the equation to calculate the number of moles of iron(II) ions in the 25 cm3 sample of iron(II) sulfate from the iron tablet.
4. Calculate the number of moles of iron(II) ions in the 250 cm3 graduated flask at the start of the experiment.
5. Calculate the mass of iron in the original five iron tablets, and hence the mass of iron in one iron tablet. Mr Fe = 55.8 g mol–1
6. Compare your value for the mass of iron with the information from the supplier about the composition of each iron tablet.
7. Make a list of any procedural errors. Suggest ways in which these errors can be avoided. 8. Calculate the percentage measurement uncertainty for the burette
Math you will find useful
Math you will find useful
Change the subject of an equation.
Substitute numerical values into algebraic equations using appropriate units for physical quantities.
Learning Tip
Learning Tip
You need two equations:
number of moles = concentration x (volume / 1000 )
number of moles = mass / Mr
Show all working carefully in a titration calculation and explain what you are doing in each step. That way you can still gain marks in an exam – even if you get the final answer wrong
C. Evaluate your Practical by Completing the Form - so you know where you should aim to make improvements in future
C. Evaluate your Practical by Completing the Form - so you know where you should aim to make improvements in future
Required Resources
Required Resources
Core Practical 11 Student Evaluation.docxCore Practical 11 - Student Sheet.docxConsult CLEAPSS Hazcards® 98A, 81, 55B. Perform a risk assessment using up-to-date information before this practical is carried out
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