Redox

Question 1

Oxidation

Answer 1

Loss of electrons, removal of hydrogen, addition of oxygen.

Question 2

Reduction

Answer 2

Gain of electrons, removal of oxygen, addition of hydrogen.

Question 3

Disproportionation

Answer 3

Where an element is both oxidised and reduced.
eg. When a copper (I) compound is added to water.
2Cu^+(aq) -> Cu^2+(aq) + Cu(s)
One Cu^+ ion oxidised to Cu^2+.
One Cu^+ ion reduced to Cu.

Question 4

Oxidising agent

Answer 4

Shown as [O]. Oxidises others, is reduced.

Question 5

Reducing agent

Answer 5

Reduces others, is oxidised.

Question 6

Oxidation number of uncombined element.

Answer 6

0

Question 7

Sum of oxidation numbers in a neutral compound

Answer 7

0

Question 8

Sum of oxidation numbers of all elements in an ion

Answer 8

Equal to the charge of the ion

Question 9

More electronegative element in a substance

Answer 9

Always given a negative oxidation number

Question 10

Oxidation number of fluorine

Answer 10

-1

Question 11

Oxidation number of hydrogen

Answer 11

+1, except when combined with less electronegative element, where it will become -1.

Question 12

Oxidation number of oxygen

Answer 12

-2, except in peroxides (-1) and with fluorine (positive).

Question 13

Example: H2S(g) + Cl2(g) -> 2HCl(g) + S(s)

Answer 13

The ox. no. of S had increased (-2 to 0), so it has been oxidised.
The ox. no. of Cl has decreased (0 to -1), so it has been reduced.
Since both oxidation and reduction have taken place the reaction is classified as a redox reaction.