Electrochemistry
Which balanced chemical equation, for an overall reaction, corresponds to this cell notation?
PbSo4(s) | SO4(aq)2- || Pt(aq)2+ | Pt(s)
(a) Pt(aq)2+ 2e- = Pt(s)
(b) PbSO4(s) + 2e- = Pb(s) + SO4(aq)2-
(c) 2HClO(aq) + H(aq)+ + 2e- = Cl2(g) + H2O(l)
To determine the balanced chemical equation that corresponds to the given cell notation, we need to understand the structure of the cell notation and the components involved.
The cell notation consists of two half-cells, separated by vertical lines. Each half-cell is represented by its reactants and products, along with their respective states (solid, liquid, or aqueous). Additionally, a double vertical line represents the salt bridge or porous barrier, which allows for ion flow to establish electrical neutrality.
Let's breakdown the cell notation given:
PbSo4(s) | SO4(aq)2- || Pt(aq)2+ | Pt(s)
The left half-cell (PbSo4(s) | SO4(aq)2-) represents a solid lead sulfate electrode immersed in an aqueous solution containing sulfate ions. In this half-cell, the anode (oxidation half-reaction) occurs.
The right half-cell (Pt(aq)2+ | Pt(s)) represents a platinum electrode immersed in a solution of platinum ions. In this half-cell, the cathode (reduction half-reaction) occurs.
To find the balanced chemical equation for the overall reaction, we need to identify the half-reactions occurring at each electrode. The anode (oxidation) half-reaction involves the loss of electrons, while the cathode (reduction) half-reaction involves the gain of electrons.
For the given half-cells:
Anode (Oxidation half-reaction): PbSo4(s) → Pb(s) + SO4(aq)2-
Cathode (Reduction half-reaction): Pt(aq)2+ + 2e- → Pt(s)
Now, let's convert these half-reactions into balanced chemical equations.
Anode (Oxidation half-reaction):
PbSo4(s) + 2e- → Pb(s) + SO4(aq)2-
Cathode (Reduction half-reaction):
Pt(aq)2+ + 2e- → Pt(s)
The balanced chemical equation for the overall reaction is obtained by multiplying the oxidation half-reaction by the number of electrons involved in the reduction half-reaction, and vice versa, so that the electrons cancel out.
By inspecting the number of electrons in each half-reaction, we see that in the oxidation half-reaction, 2 electrons are involved, and in the reduction half-reaction, 2 electrons are produced. Therefore, the half-reactions are already balanced.
Hence, the balanced chemical equation that corresponds to the given cell notation is option (b) PbSO4(s) + 2e- = Pb(s) + SO4(aq)2-.