Home

Chemistry

Global challenges

Chemical and fuel cells

Chemical and fuel cells

Videos

Summary

Exercises

Select Lesson

Exam Board

Select an option

Chemistry practicals

Investigating distillation methods

Investigating the composition of inks

Investigating acids and alkalis

Preparing soluble and insoluble salts

Investigating electrolysis

Investigating rates of reaction

Fuels and Earth science

Hydrocarbons and crude oil

Combustion and pollution

Cracking

Evolution of the Earth's atmosphere

Greenhouse gases and climate change

Rates of reaction and energy changes

Calculating rates of reactions

Catalysts

Endothermic and exothermic reactions

Energy changes in reactions

Bond energy calculations - Higher

Groups in the periodic table

Group 1: properties and reactivity

Group 7: properties and reactions

Group 0: properties and reactivity

Extracting metals and equilibria

The reactivity series of metals

Extracting metals

Biological methods of metal extraction - Higher

Reducing the use of resources

Life cycle assessments

Reversible reactions and equilibria

Position of equilibrium - Higher

Chemical changes

Acids, bases and pH

Strong and weak acids - Higher

Reactions of acids

Electrolysis

States of matter and mixtures

Changes of state

Substance types and determining purity

Filtration and crystallisation

Chromatography: phases and calculations

Potable water, treatment and purification

Key concepts

Chemical equations

Ionic equations and half equations - Higher

Hazards, risks and precautions

The history of the atom

The atom and isotopes

Calculating relative masses

Calculating relative atomic mass - Higher

The history of the periodic table

Electronic configuration

Ions and their formation

Ionic bonding: properties of compounds and naming

Covalent bonding

Giant covalent substances

Metallic bonding and alloys

Conservation of mass

Molecular and empirical formulae

Mole calculations and Avogadro's constant - Higher

Concentrations of solutions

Limiting reactants and masses - Higher

Practical skills

Measuring techniques

Safety and ethics

Designing experiments

Methods of heating substances

Working with electronics

Random sampling and sampling methods

Comparing results using percentage change

Working scientifically

The scientific method

Science communication and ethics

Evaluating risks and hazards

Collecting data

Processing and presenting data

Units and equations

Structuring a scientific report and drawing conclusions

Uncertainties and evaluations

Explainer Video

Tutor: Sophie

Summary

​Chemical and fuel cells

In a nutshell

Cells contain chemicals which react to produce electricity. The voltage produced by a cell is dependent upon a number of factors including the type of electrode and electrolyte.


Equations


word equation

symbol equation

​hydrogen→two hydrogen ions+two electronshydrogen \rightarrow two~hydrogen~ions+two~electronshydrogen→two hydrogen ions+two electrons​​
​H2→2H++2e– H_2 → 2H^+ + 2e^–H2​→2H++2e–​​
​four hydrogen ions+oxygen+four electrons→two water moleculesfour ~hydrogen~ions +oxygen+four~electrons\rightarrow two~water~moleculesfour hydrogen ions+oxygen+four electrons→two water molecules​​
​4H++O2+4e–→2H2O4H^+ + O_2 + 4e^– → 2H_2O4H++O2​+4e–→2H2​O​​
​hydrogen+oxygen→waterhydrogen+oxygen\rightarrow waterhydrogen+oxygen→water​​
​2H2+O2→2H2O2H_2 + O_2→ 2H_2O2H2​+O2​→2H2​O​​

​​​

Definitions


Electrode
An electrical metal conductor which is in contact with the electrolyte.

Electrolyte
An ionic compound which is dissolved in aqueous solution (water) or molten (melted) allowing the ions to move freely.

Cell
A cell is a system which produces electricity from chemical reactions.

Battery

A battery is two or more cells connected up together.

Redox
Reduction and oxidation.

Oxidation
Loss of electrons and gain of oxygen.

Reduction
Gain of electrons and loss of oxygen.

Anode
In fuel cells, the anode is the negative electrode. In electrolysis, the anode is the positive electrode.

Cathode
In fuel cells, the cathode is the positive electrode. In electrolysis, the cathode is the negative electrode.



Simple cells

A simple cell produces a voltage and is made up of two different electrodes dipped in an electrolyte. 

  • The two electrodes are made up of different metals.
  • The greater the difference in reactivity between the two metals, the greater the voltage.
  • Different electrolytes react with electrodes differently, which affects the magnitude of voltage.


A simple cell consists of a voltmeter connected to a negative electrode and positive electrode to measure the voltage. The two electrodes are immersed in an electrolyte.


Chemistry; Separate chemistry 1; KS4 Year 10; Chemical and fuel cells
1.
Voltmeter
2.
Negative electrode
3.
Positive electrode
4.
Electrolyte



Non-rechargeable vs chargeable batteries

In non-rechargeable batteries:

  • The reaction is irreversible
  • Reactants in the electrolyte and electrode get used up after a period of time
  • The battery cannot be re-charged

Example

Alkaline batteries


In rechargeable batteries, the battery can be recharged by applying an external electrical current to reverse the reaction.


Example

Phone batteries



Hydrogen fuel cells

Definition

Hydrogen fuel cells are electrochemical cells which produce electricity and are used as an alternative to petrol and diesel. 

Hydrogen gas from the fuel reacts with oxygen in the air:
1.
Electrical circuit
2.
Anode
3.
Acidic electrolyte
4.
Cathode
A.
Hydrogen fuel fed in at the anode.
B.
Oxygen fed in at the cathode. 
C.
Water that is produced can exit at the anode.
D.
Unreacted oxygen exits at the cathode. 


PROCEDURE 

1.
An acid is used as the electrolyte.
2.
Hydrogen fuel is oxidised at the anode to produce hydrogen ions:
 hydrogen→two hydrogen ions++two electronsH2→2H++2e–hydrogen \rightarrow two~hydrogen~ions^++two~electrons\newline H_2 → 2H^+ + 2e^–hydrogen→two hydrogen ions++two electronsH2​→2H++2e–​​
3.
The hydrogen ions migrate to the cathode, where they react with oxygen (from the air) in a reduction reaction:
 four hydrogen ions++oxygen+four electrons→two water molecules4H++O2+4e–→2H2Ofour ~hydrogen~ions^+ +oxygen+four~electrons\rightarrow two~water~molecules\newline4H^+ + O_2 + 4e^– → 2H_2Ofour hydrogen ions++oxygen+four electrons→two water molecules4H++O2​+4e–→2H2​O​​
4.
The movement of electrons from the anode to cathode produces an electrical current.
5.
The overall reaction is:
 hydrogen+oxygen→water2H2+O2→2H2Ohydrogen+oxygen\rightarrow water\newline2H_2 + O_2→ 2H_2Ohydrogen+oxygen→water2H2​+O2​→2H2​O​​


​


Advantages and disadvantages of hydrogen fuel cells 


Advantages

Disadvantages

  • Do not produce atmospheric pollutants
  • More energy efficient than petrol and diesel, as more energy is released per kilogram of fuel
  • Reduces the use and disposal of batteries
  • Exists in the gaseous state so it is difficult and expensive to store; it must be stored under high pressure which is dangerous
  • Hydrogen gas is highly explosive and flammable
  • The production of hydrogen gas usually involves energy-intense processes, such as electrolysis, which uses energy from fossil fuels


Read more

Learn with Basics

Learn the basics with theory units and practise what you learned with exercise sets!
Length:
Ions and their formation

Unit 1

Ions and their formation

Electrolysis

Unit 2

Electrolysis

Jump Ahead

Score 80% to jump directly to the final unit.

Optional

This is the current lesson and goal (target) of the path

Chemical and fuel cells

Unit 3

Chemical and fuel cells

Final Test

Test reviewing all units to claim a reward planet.

Create an account to complete the exercises

FAQs - Frequently Asked Questions

What is a battery?

A battery is two or more cells connected up together.

What is a cell?

A cell is a system which produces electricity from chemical reactions.

What is an electrolyte?

An electrolyte is an ionic compound which is dissolved in aqueous solution (water) or molten (melted) allowing the ions to move freely.

What is an electrode?

An electrode is an electrical metal conductor which is in contact with an electrolyte.

©2020 - 2024 evulpo AG

Beta