Oxidation and reduction Flashcards

1
Q

What is the definition of oxidation.

A

Oxidation – the loss of electrons.

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2
Q

What is the definition of reduction.

A

Reduction – the gain of electrons.

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3
Q

What is the definition of redox.

A

Redox – reactions in which oxidation and reduction occur simultaneously.

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4
Q

What is the definition of oxidation state

A

Oxidation state – the hypothetical charge on an atom in a compound assuming that the bonding is completely ionic.

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5
Q

What is the oxidation state of elements?

A

Elements on their own have an oxidation state of zero.

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6
Q

What is the oxidation state of a simple ion?

A

The oxidation state of a simple ion is the charge on the ion.

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7
Q

What must the oxidation states in a compound add up to?

A

The total sum of the oxidation states of all elements in a compound must add up to zero.

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8
Q

What must the oxidation states in a molecular ion add up to?

A

The total sum of the oxidation states in a molecular ion must add up to the charge on the ion.

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9
Q

What is the maximum oxidation state of an element?

A

The maximum oxidation state of an element is its group number.

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10
Q

What is the minimum oxidation state of an element?

A

The minimum oxidation state of an element is its group number -8.

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11
Q

What is the oxidation state of oxygen?

A

Oxygen has an oxidation state of -2 except in peroxides where it is -1 and in OF2 where it is +2.

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12
Q

What is the oxidation state of hydrogen?

A

Hydrogen has an oxidation state of +1 except in metal hydrides where it is -1.

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13
Q

What is the oxidation state of group 1?

A

Group 1 elements have an oxidation state of +1.

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14
Q

What is the oxidation state of group 2?

A

Group 2 elements have an oxidation state of +2.

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15
Q

What is the oxidation state of transition metals?

A

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.

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16
Q

What do ions that end in –te contain?

A

Ions which end in –te contain d or p block elements and some oxygen atoms.

17
Q

What do ions that end in –ate with the oxidation state of the positively charged ion contain?

A

The ending –ate with an oxidation state shows the oxidation state of the positively charged ion e.g. sulfate (IV) sulphur is +4.

18
Q

What do ions that end in –ate without the oxidation state of the positively charged ion contain?

A

The ending –ate without an oxidation state shows that it is the highest oxidation state e.g. sulfate is sulphur +6.

19
Q

What is an increase in oxidation state called?

A

An increase in oxidation state is oxidation.

20
Q

What is an decrease in oxidation state called?

A

A decrease in oxidation state is reduction.

21
Q

What is a redox reaction?

A

A redox reaction is one in which oxidation and reduction occur.

22
Q

What is an oxidising agent?

A

An oxidising agent causes oxidation in other species and is reduced itself.

23
Q

What is a reducing agent?

A

A reducing agent causes reduction in other species and is oxidised itself.

24
Q

What do half equations show?

A

Half equations include electrons and help show the oxidation and reduction processes in a chemical reaction.

25
Q

When oxygen is added or removed in a half equation how do you balance it?

A

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.

26
Q

What must happen to the charges in a half equation on the right and the left?

A

For all half equations the total charges on the left hand side and right hand side should be the same.

27
Q

What is the first thing you need to do when combining half equations?

A

To combine the half equations you first need to make sure that there are the same number of electrons on both sides.

28
Q

What must happen to the electrons when you combine half equations?

A

When you combine them the electrons should cancel out.

29
Q

What happens to water or hydrogen ions if they are on both sides?

A

If H2O or H+ appear on both sides they can often be cancelled down.

30
Q

What do you get when you combine half equations?

A

Combined half equations give an ionic equation.

31
Q

How are organic chemicals such as primary and secondary alcohols oxidised?

A

Organic chemicals such as primary and secondary alcohols are oxidised by acidified potassium dichromate (VI) solution.

32
Q

What happens to primary alcohols when they are oxidised?

A

Primary alcohols are oxidised to aldehydes which may be further oxidised to carboxylic acids.

33
Q

What happens to secondary alcohols when they are oxidised?

A

Secondary alcohols may be oxidised to ketones.

34
Q

How can aldehydes, ketones and carboxylic acids be reduced?

A

Aldehydes, ketones and carboxylic acid can be reduced using Lithal (LiAlH4).

35
Q

How do you represent oxidising agents in chemical reactions for organic chemicals?

A

Equations for the oxidation of organic chemicals may be written using [O] to represent the oxidising agents.

36
Q

How do you represent reducing agents in chemical reactions for organic chemicals?

A

Equations for the reduction of organic chemicals may be written using [H] to represent the reducing agent.