redox reactions

Name 4 common redox reactions

Rusting, fruits browning in air, bleach to launder clothes and use of preservative like sulfur dioxide to preserve food.

What are redox reactions?

Chemical reactions involving oxidation and reduction simultaneously.

Oxidation

The combining of a substance with oxygen,loss of hydrogens and electrons and an increase in oxidation number.

Reduction

Removal of oxygen from substance, gain of hydrogen or elections, and a decrease of oxidation number.

Oxidation number

The number of electrons lost or gained completely or partially and describes the degree of oxidation of a particular element in a compound

Name some everyday redox reactions.

Photosynthesis, respiration, combustion of coal, batteries, rusting,using bleach also known as disproportionation.

Oxidizing agent

Causes oxidation but itself is reduced in the process - therefore its oxidation state decreases.

Reducing agent

Causes reduction but itself is oxidized in the process that is its oxidation state increases.

Note!

The following are oxidizing agents

Acidified mn O4 -

Intense purple solution, when reacting with a reducing agent it turns to a colorless mn2+ ion

Acidified Cr2O7 -2

Orange cleared solution and when reacting with reducing agent it is converted to the green Chromium3+ ion

Breathalyzer test

Alcohol is a reducing agent and would react with the dichromate producing a color change proportional to the number of units of alcohol consumed.

Aqueous Fe3SO4

Light yellow when it functions as an reducing agent it becomes the pale green Fe 2+ ion

Aqueous potassium iodide

It is colour less at the beginning but turns brown as iodide molecules form until it turns black

Aqueous iron two sulphate

Pale green to pale yellow

How is bleach both an oxidizing agent and reducing agent

Alkaline solution containing sodium hypochlorite ions

Hydrogen peroxide

Used to treat cuts and bruises and bleach hair. Can act as both an oxidizing and reducing agent when reacting with a stronger of the other ra or oa. It also depends on the acidity or alkalinity

note

H2o2 decomposes on exposure to light and heat therefore it should be stored in the fridge in an amber coloured bottle. This is an example of a disproportionating reaction as the same substance is oxidized and reduced.

Sulphuric dioxide and sulphate are also known food preservatives because they inhabit oxidation of food. They can be oxidized to sulphites in this process.

Describe what is a redox titration

A type of titration classified by the reaction. A redox reaction that is not acid base take place between the titrant and titrand that are oa's and ra's.