(b)
(i) What is the lead-acid accumulator? What are the two electrodes in the charged cell of a battery and what are the two electrodes in a discharged or “flat” cell of the battery? What is the electrolyte used? [6 marks]
(ii) By writing the equations for the two chemical half reactions explain how the lead-acid accumulator works.
[4 marks]
(iii) What is the voltage that each cell of a lead-acid accumulator generates? [1 mark]
(iv) Name two factors which degrade a lead-acid accumulator’s performance. [2 marks]
(v) Detail the difference in operational mechanism of a lithium ion diffusion cell to a leadacid Cell 2.
(a) Polarography is a highly elegant technique invented by Jaroslav Heyrovsky for which he received the Nobel Prize in 1959.
(i) What is the unique feature of polarography which separates it from other electroanalytical techniques? [2 marks]
(ii) Sketch a polarogram and label two important details of the polarographic wave on your diagram. [4marks]
(b) Electrochemical or electrolytic reactions at electrodes are categorised into reversible and irreversible reactions.
(i) Why does an electrochemical process appear irreversible?[2 marks]
(ii) Explain with a sketch how the polarographic current-potential curve characterising an electrochemical process of reduction changes when the process becomes irreversible.[3 marks]
(iii) What is the potential value in mV of the separation between the anodic and cathodic peaks of a reversible one electron cyclic voltammogram? (c)
(i) Explain the principle behind the working of an ion selective electrode. [2 marks]
(ii) A glass electrode is a specific example of an ion selective electrode. How does a glass electrode work? [2 marks]
(iii) In your answer sketch a diagram of the glass electrode labelling important details in it. 3.
How might proteins such as enzymes or antibodies be modified to improve their stability or otherwise change their properties? [12 marks]
Briefly describe the biological organisms…