A common type of reference electrode comprises of silver and silver chloride, immersed in an aqueous solution of potassi

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A common type of reference electrode comprises of silver and silver chloride, immersed in an aqueous solution of potassium chloride (Ag|AgCl|KCl).
a) Why is a reference electrode required in many electrochemical experiments?
b) In the case of the silver-silver chloride reference electrode, the equilibrium can be written as Ag + Cl- ＝ AgCl + e-. Write down the Nernst equation for the reaction of Ag/Ag+ redox-reaction in the absence of chloride ions, using the standard reduction potential EAg+|Ag0=0.800 VSHE.
c) AgCl is poorly soluble in water and the activities of silver and chloride ions are related through the solubility product K = a(Ag+) · a(Cl-) = 1.76 · 10-10. Make use of this to re-write the Nernst equation from (b) in a sum of a constant term and a term depending on the chloride activity a(Cl-).
d) At room temperature and in a saturated KCl solution, a(Cl-) ≈ 2.7. What is the reversible potential of the silver-silver chloride reference electrode in that solution?