Standard electrode potentials
| English | Chinese | Pinyin |
|---|---|---|
| electrode potential | 电极电势 | diàn jí diàn shì |
| half-cell | 半电池 | bàn diàn chí |
| cell potential | 电池电势 | diàn chí diàn shì |
| standard hydrogen electrode | 标准氢电极 | biāo zhǔn qīng diàn jí |
| oxidising agent | 氧化剂 | yǎng huà jì |
| reducing agent | 还原剂 | huán yuán jì |
Ranking the electron-grabbers
- The electrode potential 电极电势 $E$ shows how easily a half-cell 半电池 is reduced.
- We measure it against a fixed reference under standard conditions.
- Combining two half-cells gives a cell potential 电池电势.
Electrode potential lab
Ecell = Eright - Eleft
Change cell potential and see oxidising power increase.
A more negative standard electrode potential means a stronger reducing agent.
It loses electrons more readily.
The reference and measuring E°
- The standard hydrogen electrode 标准氢电极 is the zero reference: $\text{H}_2$ at 1 atm over platinum in $1\ \dfrac{\text{mol}}{\text{dm}^3}$ $\text{H}^+$, defined as 0.00 V.
- To measure a half-cell's $E^{\ominus}$, connect it to the hydrogen electrode and read the voltage (always written as a reduction).
The electrochemical series of standard electrode potentials
The standard hydrogen electrode is defined as having a potential of:
It is the reference half-cell, set at exactly 0.00 V; all other E° values are measured against it.
Match each electrode-potential idea.
Each item links the term to its correct meaning.
Combining half-cells
- Polarity: the more negative electrode is the negative terminal; electrons flow from it through the circuit.
- Reactivity: a more positive $E^{\ominus}$ → better oxidising agent 氧化剂; a more negative $E^{\ominus}$ → better reducing agent 还原剂.
Electrolysis electroplates an object with a thin, shiny layer of metal such as chromium.
The standard cell potential is:
Subtract the less positive electrode potential from the more positive one.
A half-cell with a more positive E° is:
A more positive E° means the species is readily reduced — a stronger oxidising agent.
In a cell, electrons flow through the external circuit from the:
The more negative electrode is the negative terminal; electrons flow from it to the more positive electrode.
Reading the electrode-potential table
- The more positive E°, the more easily the species is reduced (a stronger oxidising agent).
- The more negative, the stronger the reducing agent.
The standard hydrogen electrode reference
You've got it
- $E^{\ominus}$ shows how easily a half-cell is reduced (written as a reduction)
- the standard hydrogen electrode = 0.00 V reference
- $E^{\ominus}_{\text{cell}} = E^{\ominus}(\text{more positive}) - E^{\ominus}(\text{less positive})$
- more positive $E^{\ominus}$ = stronger oxidising agent; more negative = stronger reducing agent