CHEMISTRY UNIT 1 Oxidising and reducing agents

Oxidising and reducing agents

What is reduction ?

Reduction is a gain of electrons by a reactant in any reaction

What is oxidation ?

Oxidation is a loss of electrons by a reactant in any reaction

What is a redox reaction ?

A redox reaction is a reaction in which reduction and oxidation take place at the same time

What is a oxidising agent ?

An oxidising agent is a substance that accepts electrons 

What is a reducing agent ?

A reducing agent is a substance that donates electrons

In what type of reaction can oxidising and reducing agents be identified in ?

Oxidising and reducing agents can be identified in redox reactions

What are the traits of a reducing agent ?

• is usually a metal of negative ion

• donates (loses) electrons to another element or ion (reducing the other species)

• I itself oxidised

What are the traits of an oxidising agent ?

• is normally a non-metal or positive ion

• cause oxidation reactions to take place

• gains electrons from other atoms or ions (is itself reduced)

What is are examples of an oxidising agent ?

• hydrogen peroxide is a molecule that is an oxidising agent 

• dichromate and permanganate ions are group ions that are strong oxidising agents in acidic solutions 

What is an example of a reducing agent ?

Carbon monoxide (CO) is a gas that can be used as a reducing agent

Why are oxidising agents used widely ?

Oxidising agents are widely used because of their effectiveness with which they can kill fungi and bacteria, and can inactivate viruses. The oxidation process is also an effective means of breaking dow coloured compounds, making oxidising agents ideal for use as ‘bleach’ for clothes and hair

What is an example of a use of oxidising agents and why ?

Oxidising agents can be used as ‘bleach’ for clothes and hair as the oxidation process is an effective means of breaking down coloured compounds

What does the electrochemical series represent ?

The electrochemical series represents a series of reduction reactions

Where are the strongest oxidising agents located in the electrochemical series ?

The strongest oxidising agents are at the bottom of the left-hand column of the electrochemical series

Where are the strongest reducing agents located on the electrochemical series 

The strongest reducing agents are at the top of the right-hand column of the electrochemical series 

Why do elements with low electronegativities act as reducing agents ?

Elements with low electronegativites tend to form ions by losing electrons and so act as reducing agents

Why do elements with high electronegativites act as oxidising agents ?

Elements with high electrogenativities tend to form ions by gaining electrons and so act as oxidising agents

How can equations for redox reactions be produced ?

Equations for redox reactions can be produced by adding together the two ion-electron equations representing each half-step (either reduction or oxidation)

What type of reaction is a good example of redox reactions and why ?

Displacement reactions are good examples of redox reactions as metals higher in the electrochemical series will displace lower metals from a solution of their ions which means that the higher metal is oxidised (loses electrons) and the lower metal is reduced (gains electrons)

What is a spectator ion ?

A spectator ion is an ion that is present in the reaction but remains unchanged at the end (doesn’t participate)

What period in the periodic table are the strongest reducing agents found ?

The strongest reducing agents are in group 1

Where are the strongest oxidising agents found in the periodic table ?

The strongest oxidising agents are in group 7

What is a standard solution ?

A standard solution is a solution of accurately known concentration

What is determined by a titration ?

The volume (measured to 1 decimal place) of a reactant solution required to complete the reaction is determined by titration.

What is the requirement for solutions to be considered concordant ?

The solution volumes must be within 0.2cm3 of each other to be considered concordant 

What happens to the oxidising agent itself during a redox reaction ?

During a redox reaction the oxidising agent itself is reduced

What happens to the reducing agent itself during a redox reaction ?

During a redox reaction the reducing agent itself is oxidised

What are the steps to preparing a standard solution ? (detailed)

• A known mass of solid sample is measured and added to a beaker (see measuring substances accurately)

• Deionised water is added to the beaker to dissolve the solute

• Carefully add the solution to the standard flask (volumetric flask)

• Rinse out the beaker several times with deionised water and add the washings to the standard flask

• Add deionised water to the standard flask to bring the volume of the solution up to the graduation mark on the neck of the flask. The meniscus should be at the graduation mark on the flask

• Stopper the flask and invert several times to ensure the solution is mixed thoroughly

In titrations involving iodine what indicator will be used ?

In titrations involving iodine starch will be used as an indicator