What is a galvanic cell? Give the half-cell reactions of a Daniell cell and explain a redox couple.

(N/A) Galvanic cell: It is an electrochemical cell that converts the chemical energy of a spontaneous redox reaction into electrical energy.
$(b)$ Chemical reactions in a Daniell cell:
$(i)$ $Cu^{2+}_{(aq)} + 2e^{-} \longrightarrow Cu_{(s)}$ (reduction half-reaction)
$(ii)$ $Zn_{(s)} \longrightarrow Zn^{2+}_{(aq)} + 2e^{-}$ (oxidation half-reaction)
$(iii)$ $Zn_{(s)} + Cu^{2+}_{(aq)} \longrightarrow Zn^{2+}_{(aq)} + Cu_{(s)}$ (overall redox reaction)
These reactions occur in two different portions of the Daniell cell. The reduction half-reaction occurs on the copper electrode,while the oxidation half-reaction occurs on the zinc electrode. These two portions are called half-cells. $A$ redox couple is defined as having together the oxidized and reduced forms of a substance taking part in an oxidation or reduction half-reaction. For example,$Zn^{2+}/Zn$ and $Cu^{2+}/Cu$ are redox couples.