Question

(a) (i) Explain the thermodynamics of cell reactions.
(ii) Why salt bridge is used in Galvanic cells?

Hint:

A useful way to remember the spontaneity of a cell: If Eₑₓtcₑll is positive, Δ G is negative, meaning the reaction is spontaneous and the cell acts as a Galvanic cell. If Eₑₓtcₑll is negative, Δ G is positive, and the reaction requires an external power source, characteristic of an Electrolytic cell.

Answer 1

(i) Reaction with Cl₂ in light:
In the presence of light, chlorine undergoes free radical substitution. All hydrogen atoms are eventually replaced by chlorine to form perchlorodiethyl ether. CH₃CH₂OCH₂CH₃ + 10Cl₂ hv CCl₃CCl₂OCCl₂CCl₃ + 10HCl (Note: In the dark, only the α-hydrogens are replaced to form 1,1'-dichlorodiethyl ether).
(ii) Reaction with dil H₂SO₄:
Heating diethyl ether with dilute sulphuric acid under pressure results in hydrolysis, converting it into ethanol. C₂H₅OC₂H₅ + H₂O dil. H₂SO₄, Δ 2C₂H₅OH
(iii) Reaction with CH₃COCl and anhydrous ZnCl₂:
Diethyl ether reacts with acetyl chloride in the presence of anhydrous ZnCl₂ to form ethyl acetate and ethyl chloride. CH₃COCl + C₂H₅OC₂H₅ anh. ZnCl₂ CH₃COOC₂H₅ + C₂H₅Cl