the two half-reactions that are used in the direct methanol fuel cell are shown below.
I. 2 CH3OH(aq)+2H2O(l)=>2CO2(g)+12H+(aq)+12e-
II. 3O2(g)+12H+(aq) +12e-=>6H2O(l)
the electrode at which half-reaction I occurs is the ______ at which______ is oxidized, and half-reaction II occurs at the ______ at which ________ is reduced.
need help with the blanks!
I won't fill in the blanks but here is the information you need to answer.
Oxidation occurs at the anode; reduction occurs at the cathode.
Oxidation is the loss of electrons; reduction is the gain of electrons. In reaction i I see C(in methanol) changing from an oxidation state of -2 to +4(in CO2) for each methanol.
In reaction ii I see O going from zero on the left to -2 on the right.
The electrode at which half-reaction I occurs is the anode, and at this electrode, methanol is oxidized.
The half-reaction II occurs at the cathode, and at this electrode, oxygen is reduced.
To determine the electrode at which each half-reaction occurs and the species being oxidized or reduced, we need to identify the oxidation and reduction reactions.
In the given half-reactions:
I. 2 CH3OH(aq) + 2 H2O(l) => 2 CO2(g) + 12 H+(aq) + 12 e-
II. 3 O2(g) + 12 H+(aq) + 12 e- => 6 H2O(l)
Half-reaction I involves the conversion of methanol (CH3OH) to carbon dioxide (CO2) along with the generation of protons (H+) and electrons (e-). In this reaction, methanol is being oxidized since it loses electrons.
Therefore, the electrode at which half-reaction I occurs is the anode (negative electrode) and methanol is oxidized at this electrode.
Half-reaction II involves the reduction of oxygen gas (O2) to water (H2O) accompanied by the consumption of protons (H+) and electrons (e-). In this reaction, oxygen is being reduced since it gains electrons.
So, the electrode at which half-reaction II occurs is the cathode (positive electrode) and oxygen is reduced at this electrode.
In summary:
- Half-reaction I occurs at the anode, where methanol (CH3OH) is oxidized.
- Half-reaction II occurs at the cathode, where oxygen (O2) is reduced.