Oxidation and reduction Flashcards
What is the definition of oxidation.
Oxidation – the loss of electrons.
What is the definition of reduction.
Reduction – the gain of electrons.
What is the definition of redox.
Redox – reactions in which oxidation and reduction occur simultaneously.
What is the definition of oxidation state
Oxidation state – the hypothetical charge on an atom in a compound assuming that the bonding is completely ionic.
What is the oxidation state of elements?
Elements on their own have an oxidation state of zero.
What is the oxidation state of a simple ion?
The oxidation state of a simple ion is the charge on the ion.
What must the oxidation states in a compound add up to?
The total sum of the oxidation states of all elements in a compound must add up to zero.
What must the oxidation states in a molecular ion add up to?
The total sum of the oxidation states in a molecular ion must add up to the charge on the ion.
What is the maximum oxidation state of an element?
The maximum oxidation state of an element is its group number.
What is the minimum oxidation state of an element?
The minimum oxidation state of an element is its group number -8.
What is the oxidation state of oxygen?
Oxygen has an oxidation state of -2 except in peroxides where it is -1 and in OF2 where it is +2.
What is the oxidation state of hydrogen?
Hydrogen has an oxidation state of +1 except in metal hydrides where it is -1.
What is the oxidation state of group 1?
Group 1 elements have an oxidation state of +1.
What is the oxidation state of group 2?
Group 2 elements have an oxidation state of +2.
What is the oxidation state of transition metals?
Transition metals vary. The number in roman numerals in the name gives the oxidation state of the transition metal ion. E.g. Potassium manganate (VII) shows the manganese ion is +7.
What do ions that end in –te contain?
Ions which end in –te contain d or p block elements and some oxygen atoms.
What do ions that end in –ate with the oxidation state of the positively charged ion contain?
The ending –ate with an oxidation state shows the oxidation state of the positively charged ion e.g. sulfate (IV) sulphur is +4.
What do ions that end in –ate without the oxidation state of the positively charged ion contain?
The ending –ate without an oxidation state shows that it is the highest oxidation state e.g. sulfate is sulphur +6.
What is an increase in oxidation state called?
An increase in oxidation state is oxidation.
What is an decrease in oxidation state called?
A decrease in oxidation state is reduction.
What is a redox reaction?
A redox reaction is one in which oxidation and reduction occur.
What is an oxidising agent?
An oxidising agent causes oxidation in other species and is reduced itself.
What is a reducing agent?
A reducing agent causes reduction in other species and is oxidised itself.
What do half equations show?
Half equations include electrons and help show the oxidation and reduction processes in a chemical reaction.
When oxygen is added or removed in a half equation how do you balance it?
If oxygen atoms are added or removed from a compound or ion H2O and hydrogen ions H+ are used to balance this change in oxygen content.
What must happen to the charges in a half equation on the right and the left?
For all half equations the total charges on the left hand side and right hand side should be the same.
What is the first thing you need to do when combining half equations?
To combine the half equations you first need to make sure that there are the same number of electrons on both sides.
What must happen to the electrons when you combine half equations?
When you combine them the electrons should cancel out.
What happens to water or hydrogen ions if they are on both sides?
If H2O or H+ appear on both sides they can often be cancelled down.
What do you get when you combine half equations?
Combined half equations give an ionic equation.
How are organic chemicals such as primary and secondary alcohols oxidised?
Organic chemicals such as primary and secondary alcohols are oxidised by acidified potassium dichromate (VI) solution.
What happens to primary alcohols when they are oxidised?
Primary alcohols are oxidised to aldehydes which may be further oxidised to carboxylic acids.
What happens to secondary alcohols when they are oxidised?
Secondary alcohols may be oxidised to ketones.
How can aldehydes, ketones and carboxylic acids be reduced?
Aldehydes, ketones and carboxylic acid can be reduced using Lithal (LiAlH4).
How do you represent oxidising agents in chemical reactions for organic chemicals?
Equations for the oxidation of organic chemicals may be written using [O] to represent the oxidising agents.
How do you represent reducing agents in chemical reactions for organic chemicals?
Equations for the reduction of organic chemicals may be written using [H] to represent the reducing agent.
