A balanced equation that represents an overall cell reaction is shown. Choose the cell notation which corresponds to the electrochemical cell that is described by this equation.
2H2O(l) → 2H2(g) + O2(g)
i don't get why the answer is this. How can OH- appear in both sides
Pt(s) | OH-(aq) | O2(g) || OH-(aq), H2O(l) | H2(g), Pt(s)
The left hand cell is
2OH^- ==> O2 + 4e + 2H^+
The right hand cell is
4H^+ + 2e + 2OH^- ==> H2 + 2H2O
The balanced equation given is:
2H2O(l) → 2H2(g) + O2(g)
To understand why the cell notation includes OH- on both sides, let's break down the half-reactions involved in the balanced equation:
Half-reaction 1 (oxidation): 2H2O(l) → O2(g) + 4H+(aq) + 4e-
Half-reaction 2 (reduction): O2(g) + 4Oh-(aq) + 4e- → 2H2O(l)
In the first half-reaction, water molecules (H2O) are oxidized to produce oxygen gas (O2), as well as four hydrogen ions (H+) and four electrons (e-).
In the second half-reaction, oxygen gas (O2) reacts with hydroxide ions (OH-) to produce water molecules (H2O), along with four electrons (e-).
By combining these two half-reactions, we can see that OH- appears on both sides of the overall balanced equation. This means that OH- is involved during the reduction half-reaction, where it reacts with O2 to produce H2O.
The cell notation is written as follows:
Pt(s) | OH-(aq) | O2(g) || OH-(aq), H2O(l) | H2(g), Pt(s)
In this notation, the vertical lines (|) represent the different phases of the components, the double vertical lines (||) represent the salt bridge or separator, and the left side of the double vertical lines represents the oxidation half-reaction while the right side represents the reduction half-reaction.
So, in the given cell notation, OH- appears on both sides to indicate the presence of hydroxide ions in the reduction half-reaction, where they react with O2 to produce H2O.