Topic 3- Redox 1

Question 1

know what is meant by the term ‘oxidation number’

Answer 1

Tells you how many electrons an atom has donated or accepted to form an ion

Question 2

be able to calculate the oxidation number of elements in compounds and ions The use of oxidation numbers in peroxides and metal hydrides is expected.

Answer 2

-unconvinced elements have an oxidation number of 0 -monatomic ion is the same as its charge -molecular ion has the sum of its overall charge ie 02 =-4 -neutral compounds have an overall charge of0 - H =+1 except in metal hydrides where it’s -1 or in H2 where it’s 0 0 is -2 except in peroxide’s where it’s -1 and 02 where it’s 0

Question 3

understand oxidation and reduction in terms of electron loss or electron gain

Answer 3

OILRIG (oxidation is loss reduction is gain )

Question 4

know that oxidising agents gain electrons know that reducing agents lose electrons

Answer 4

Oxidising agents accept electrons and get reduced Reducing agent donates electrons and gets oxidised.

Question 5

understand oxidation and reduction in terms of electron transfer and changes in oxidation number, applied to reactions of s- and p-block elements

Answer 5

When metals form compounds they donate electrons to form positive ions and their oxidation number increases When non metals form compounds they gain electrons to form negative ions and oxidation number decreases

Question 6

understand that a disproportionation reaction involves an element in a single species being simultaneously oxidised and reduced know that oxidation number is a useful concept in terms of the classification of reactions as redox and as disproportionation

Answer 6

Cl2 + 2OH- >ClO- + Cl- +H20 Chlorine goes to -1 and +1 showing this is a disproportionation reaction.

Question 7

be able to indicate the oxidation number of an element in a compound or ion, using a Roman numeral

Answer 7

Oxidation numbers can be shown my Roman numerals eg copper (ll) has an oxidation number of +2

Question 8

be able to write formulae given oxidation numbers

Answer 8

Unless told assume overall charge is 0 Need to work out ratio of cations to anions Balance it to equal the overall charge you want.

Question 9

understand that metals, in general, form positive ions by loss of electrons with an increase in oxidation number understand that non-metals, in general, form negative ions by gain of electrons with a decrease in oxidation number

Answer 9

When metals form compounds they donate electrons to form positive ions and their oxidation number increases When non metals form compounds they gain electrons to form negative ions and oxidation number decreases

Question 10

be able to write ionic half-equations and use them to construct full ionic equations

Answer 10

Question 11

be able to write ionic half-equations and use them to construct full ionic equations using h+, e- and h20

Answer 11