Voltage from two metals of different reactivity, batteries, rechargeable cells, and the hydrogen fuel cell.
What you will learn
- Predict the voltage of a simple cell from reactivity data
- Explain why non-rechargeable cells stop
- Evaluate hydrogen fuel cells against batteries
Two metals, one voltage
Two different metals in an electrolyte make a cell.
The more reactive metal is the negative electrode. The bigger the difference in reactivity, the bigger the voltage.
- magnesium against copper: 2.7 V; zinc against copper: 1.1 V
- magnesium against zinc: 2.7 − 1.1 = 1.6 V
A battery is two or more cells in series: the voltages add. A non-rechargeable cell stops when a reactant is used up; a rechargeable one is reversed by an external current.
The voltage of a cell depends on which two metals are the electrodes and on the electrolyte.
The rest of this lesson and its 11 practice questions are locked.
In this lesson
- Two metals, one voltage
- The hydrogen fuel cell
11 practice questions, marked as you go; about 20 minutes in all.
Key terms
Cell, Battery
In this unit: Energy changes
Exothermic and endothermic reactions, the temperature change practical, reaction profiles, bond energies, cells and fuel cells.
- Exothermic and endothermic reactions
- Required practical: temperature changes
- Reaction profiles
- Bond energies
- Chemical cells and fuel cells