Question

How may chemical reactions be used to generate electricity? Do all batteries work on the basis of harnessing the energy of chemical reactions and converting this energy into electricity? Provide several examples.

Answer 1

The electrochemical cells are used in generating electricity by converting the energy produced from the chemical reaction occurring at the electrodes.

Examples:

1) The galvanic cell (an example of the electrochemical cell), i.e. Zn/Zn2+//Cu2+/Cu

The reaction at anodic half-cell: Zn(s) Zn²⁺(aq) + 2e^- (Oxidation at anodic half-cell), (E^o_Zn²⁺/?Zn)_anode = -0.76 V

The reaction at cathodic half-cell: Cu²⁺(aq)? ?+ 2e^- Cu(s) (Reduction at cathodic half-cell), (E^o_Cu²⁺/Cu)_cathode = 0.34 V

The overall cell reaction is Zn(s) + Cu²⁺(aq)? Zn²⁺(aq)? + Cu(s), (E^o)_cell = (E^o_Cu²⁺/Cu)_cathode ? ?- (E^o_Zn²⁺/?Zn)_anode ?= 0.34-(-0.76) = 1.1 V

2) Cu/Cu²⁺//Ag⁺/Ag

The reaction at anodic half-cell: Cu(s) Cu²⁺(aq) + 2e^- (Oxidation at anodic half-cell), (E^o_Cu²⁺/Cu)_anode = 0.34 V

The reaction at cathodic half-cell: 2Ag⁺(aq)? + 2e^- 2Ag(s) + 2e^- (Reduction at cathodic half-cell), (E^o_Ag⁺/Ag)_cathode = 0.8 V

The overall cell reaction is Zn(s) + Cu²⁺(aq)? Zn²⁺(aq)? + Cu(s), (E^o)_cell = ?(E^o_Ag⁺/Ag)_cathode ?- (E^o_Cu²⁺/Cu)_anode ?= 0.80-(0.34) = 0.46 V