You're always going to get a question on one of the PPA's, so if you know the answers to these then you're, to quote my Maths teacher, flying by the seat of your pants. Or something.
PPA1 - the effect of concentration changes on reaciton rate
Aim: The aim is to find the effect of varying the concentration of iodide ions on the rate of reaction between hydrogen peroxide and acidified potassium iodide solution.
a) Suggest a method for measuring the rate of this reaction
b) The experiment was carried out to investigate the effect of iodide ion concentration on reaction rate. Suggest two factors which should be kept constant throughout the experiment.
c) How is the course of reaction followed?
d) Suggest any safety precautions which should be carried out.
PPA2 - the effect of temperature changes on reaction rate
Aim: The aim is to find the effect of varying temperature on the rate of reaction between oxalic acid and an acidified solution of potassium permanganate.
a) Suggest an experiment to investigate the effect of temperature on the reaction rate - can you name the acid used?
b) Suggest two factors which should be kept constant throughout the experiment.
c) How is the course of the reaction followed?
d) What are the units of reaction rate?
e) Suggest any safety precautions which should be carried out.
PPA3 - The Enthalpy of Combustion
Aim: The aim is to determine the enthalpy of combustion of ethanol.
a) Draw a diagram of the apparatus you would use
b) List all the safety precautions you should take
c) The experimental value is often much less than the data book value. Give two reasons for this, including one which is not related to heat loss to the surroundings.
Unit 2
PPA 1 - Oxidation
Aim: The aim is to use the mild oxidising agents (acidified potassium dichromate solution, Benedict's solution and Tollen's reagent) to distinguish between two given carbonyl compounds, one of which is an aldehyde, the other a ketone.
a) Name suitable oxidising agents and be able to give the colour change involved when they react.
b) Why is the potassium dichromate acidified?
c) List all the safety precautions you should take
PPA2 - making esters
Aim: The aim is to prepare and ester and identify some of the characteristic properties of esters.
a) Describe the function of the sulphuric acid.
b) Draw a diagram to show how you would heat the mixture
c) Mention any necessary safety precautions
d) Describe how you would detect the presence of an ester
e) It was stated that some of the reaction mixture would be lost through evaporation during heating. Make an addition to your diagram to show how this could be reduced.
PPA3 - Factors affecting enzyme activity
Aim: The aim is to investigate the effect of pH or temperature changes on enzyme activity.
a) Suggest a method for measuring enzyme activity of an enzyme under conditions of varied pH or temperature.
b) What measurements would you take?
c) What form would the resulting graph of pH/temperature against enzyme activity take?
Unit 3
PPA1 - Hess's Law
Aim : The aim of the experiment is to confirm Hess's law.
a) What measurements must be taken at each stage?
b) Explain why a plastic beaker is preferable to a metal one.
c) List any safety precautions you would take.
d) Before adding together the solutions of acid and alkali, how is the initial temperature determined?
PPA2 - Quantative Electrolysis
Aim: The aim is to confirm the reaction 2H+(aq) + 2e ----> H2(g), that is to determine the quantity of electricity required to produce one mole of hydrogen by electrolysing dilute sulphuric acid.
a) Draw a diagram of the apparatus used.
b) In order to find the quantity of electricity in order to produce one mole of hydrogen by electrolysis, what measurements have to be made?
c) List any safety precautions you would take.
PPA3 - A Redox Titration
Aim: The aim is to determine the mass of vitamin C in a tablet by carrying out a redox titration using a solution of iodine of accurately known concentration and starch solution as an indicator.
a) What is meant by a standard solution and how can one be prepared?
b) How could the end point of the titration be determined?
c) List an apparatus needed for such a titration.
d) From the results of several titrations, including a rough one, what volume of solution would be used in the calculation?
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Edited by Ally, 29 January 2006 - 05:48 PM.