Topic 6.1 Redox And Oxidation State (number)

Question 1

Oxidation involves the ____ of electrons

Reduction involves the ____ of electrons

Answer 1

Oxidation involves the loss of electrons

Reduction involves the gain of electrons

Question 2

What reaction involves the transfer of electrons

Answer 2

A redox reaction involves the transfer of electrons

Question 3

An oxidising agent ____ electrons form another species. (I.e. ____)

An reducing agent ____ electrons form another species. (I.e. ____)

Answer 3

An oxidising agent removes electrons form another species.
(I.e. it oxidises other things)

An reducing agent gives electrons form another species. (I.e. it reduces other things)

Question 4

Rule for half equations:

Answer 4

When oxidation occurs, electrons are written after the arrow.
When reduction occurs, electrons are written before the arrow.

e- on right hand side of arrow when ox

e- on left side when reduced

Question 5

Half equations:

The reaction between Zinc and Copper can be written as two half equations to show what happens to each species in the reaction:

Answer 5

Ox). Zn —> Zn^2+ + 2e^-

Red). Cu^2+ + 2e^- —> Cu

Question 6

Balancing redox equations:

How do you write balanced redox equations?

Answer 6

You write an equation so that the electrons cancel out

This is, the number of electrons being lost must equal the number of electrons being gained

Question 7

Oxidation Numbers
(oxidation states)

What is an oxidation number?

Answer 7

Page 10 of booklet

Question 8

What the general rule of oxidation numbers?

Answer 8

If the oxidation number of an atom or molecule increases (or becomes more positive ) then oxidation has occurred

If the oxidation number of an atom or molecule decreases (orbecomes more negative) then reduction has occurred.

Question 9

Rules for calculating oxidation numbers (5)

Answer 9

1) In elements, the oxidation number (O.N) is always 0

2) the O.N. Of an ion of an element is the same as it’s ionic charge (in most cases)

3) in a neutral species (covalent or ionic) the elements take on an oxidation number as if they were changed

4) covalent molecules are assumed to be ionic

5) molecular ions; the sum of the oxidation states of the elements present must be equal to the charge on the ion

Question 10

When writing oxidation numbers, where do you place the negative/positive sign? Before or after the number?

Answer 10

Before the number

Question 11

Rule 3 guide…

Question 12

3 - covalent species

Question 13

4

Question 14

Concept of ox (pg13)