Section 4 redox Flashcards
Oxidation definition
An oxidation is a loss of electrons from reactants in a reaction.
Reduction definition
A reduction is a gain of electrons by reactants in a reaction.
Page of the data booklet you need for ion electron equations
The electrochemical series
How do you identify if a reaction is an oxidation
The electrons are at the end of the equation. (Therefore being lost from reactants)
How do you tell if a reaction is a reduction reaction
The electrons are at the start of the reaction (therefore being gained by the reactants.)
When writing down an oxidation ion electron equation always remember
To flip the ion electron equation
And if with a reduction reaction make sure it is higher on the electrochemical series.
When writing down a reduction ion equation always remember
To keep the equation the same way round,
To make sure that the equation is lower than the oxidation.
Redox reaction definition
A reaction where both a reduction and an oxidation occur.
How do you produce a redox equation
You have to balance the number of electrons on each reaction
Then you must cancel out the electrons and any other shared chemicals.
Then you combine the reaction.
Oxidising agent definition
A substance that oxidises another substance, and itself is reduced, meaning it is an electron acceptor /oxygen donor /hydrogen acceptor.
Reducing agent definition
A substance that reduces another substance, it itself will undergo oxidation, meaning it is an electron donor/ oxygen acceptor/ hydrogen donor.
Where are oxidising agents found on the electrochemical series
The bottom left hand column
Where are the strongest reducing agents found in the electrochemical series
At the top of the right hand column
Where are strong oxidising agents found on the periodic table
In the halogens / group 7
Where are strong reducing agents found on the periodic table
On the alkali metals / group one of the periodic table .
Reducing agents I need to know
Carbon monoxide
Oxidising agents I need to know
Hydrogen peroxide (H2O2)
Dichromate (Cr207 2-)
permanganate Mn04-
What must be added to oxidising agents
Acid - to supply hydrogen ions
Why must acid be added to oxidising agents
To supply hydrogen ions.
Features of oxidising agents
Occur when there is a:
Gain of electron
Loss of oxygen
Gain of hydrogen
Reducing agents features
Reducing agents:
Lose electrons
Gain oxygen
Lose hydrogen
Metal atoms to ions
Go from neutral to positively charged, meaning they lose electrons, meaning they are oxidised and reducing agents.
Metal ions to metal atoms
Go from positively charged to neutral so they gain electrons, meaning they are reduced and the oxidising agent.
Non metal atoms to non metal ions
Go from neutral to negative, so gain electron, undergoing reduction and becoming an oxidising agent.
Non metal ions to non metal atoms
Go from negatively charged to neutral, therefore are losing electrons, meaning they are oxidised and the reducing agent.
Writing ion electron equations from scratch stages
Balance number of non oxygen atoms
Add water to one side balancing oxygen
Add hydrogen + to the other to balance out hydrogen
Add electrons to cancel out the difference in charge.
Uses of oxidising agents
Sodium hypochlorite is used to kill fungi, bacteria and viruses.
Potassium permanganate is used in killing bacterial infections in fish.
Hydrogen peroxide is used in bleaching clothes and hair. (By breaking down colour compounds.
Why may an indicator not be necessary when doing a redox titration
It may be self indicating
Titration technique and skills
Must use a standard flask when measuring out a standard solution,
The burette must be at eyesight
The burette must be rinsed through before the titration begins
The burette must have a filter funnel in the top to pour liquid in and removed when the titration is happening
A white object like paper should be put under the conical flask to easily determine the end point
A rough titre must be used
The results should be concordant.
Conical flask must be swirled throughout titrations.
Concordant results
Results within 0.2 cm3 of each other.
Calculating a redox titration. When finding mass
Use N=CV
Then mole ratio
M =n times GFM
Then multiply to sample.
Calculating redox titration when finding concentration.
N=CV
MOLE RATIO
C=N/V OR V=N/C
Explain why a substance is a reducing agent
The chemical loses electrons / gains oxygen / loses hydrogen, meaning that the chemical is being oxidised, therefore reducing another substance and therefore is a reducing agent.
Explain why a substance is an oxidising agent
There is a gain of electrons/ loss of oxygen / gain of hydrogen, meaning that the substance is oxidising another substance and is being reduced therefore the substance is an oxidising agent.
