What is Electrochemistry?
Electrochemistry is the branch of chemistry that studies the connection between chemical reactions and electricity — how redox reactions can generate electric current, or how electric current can drive a chemical reaction.
Electrochemistry studies redox (oxidation-reduction) reactions that produce or consume electrical energy, using cell potential E°cell = E°cathode − E°anode to predict whether a reaction is spontaneous.
- •Spontaneous redox reaction (E°cell > 0)
- •Converts chemical energy → electrical energy
- •Anode is negative, cathode is positive
- •Used in batteries
- •Non-spontaneous reaction (E°cell < 0)
- •Converts electrical energy → chemical energy
- •Anode is positive, cathode is negative
- •Used in electroplating and electrolysis
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Step-by-step worked examples
A Zn/Cu cell has E°(Cu²⁺/Cu) = +0.34 V (cathode) and E°(Zn²⁺/Zn) = −0.76 V (anode). Find E°cell.
E°cell = E°cathode − E°anode E°cell = 0.34 − (−0.76) E°cell = 1.10 V
An Ag/Zn cell has E°cathode(Ag⁺/Ag) = +0.80 V and E°anode(Zn²⁺/Zn) = −0.76 V. Find E°cell.
E°cell = E°cathode − E°anode E°cell = 0.80 − (−0.76) E°cell = 1.56 V
In Cu²⁺ + 2e⁻ → Cu, how many moles of Cu deposit when 2 mol of electrons pass through the cell?
2 mol e⁻ are needed to deposit 1 mol Cu (from the balanced half-reaction) moles Cu = 2 mol e⁻ ÷ 2 moles Cu = 1 mol
Flashcards
Quick quiz
Q1.Oxidation occurs at the:
Q2.A positive E°cell indicates the reaction is:
Q3.The formula for standard cell potential is:
Q4.In a galvanic cell, electrons flow through the external circuit from:
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Common mistakes
Reduction happens at the anode. — Correct: Reduction happens at the cathode; oxidation happens at the anode (mnemonic: An Ox, Red Cat).
Electron flow and conventional current flow in the same direction. — Correct: Electrons flow anode → cathode; conventional current flows the opposite direction through the external circuit.
All electrochemical cells are spontaneous. — Correct: Galvanic cells are spontaneous (E°cell > 0); electrolytic cells are non-spontaneous and need an external power source.
Cell potential doesn't depend on which electrode is labeled cathode vs anode. — Correct: Swapping the cathode/anode assignment flips the sign of E°cell.
FAQ
What is electrochemistry?
It's the branch of chemistry studying how redox reactions produce electricity, and how electricity can drive chemical reactions.
What is the formula for cell potential?
E°cell = E°cathode − E°anode, using standard reduction potentials.
How do you calculate standard cell potential (E°cell)?
Subtract the anode's standard reduction potential from the cathode's standard reduction potential.
What are examples of electrochemistry in real life?
Batteries, electroplating, corrosion of metals, and fuel cells are all everyday electrochemistry.