topic 3: redox 1

Question 1

oxidation (in terms of electrons)

Answer 1

loss
- increase in oxidation number

Question 2

reduction (in terms of electrons)

Answer 2

gain
- decrease in oxidation number

Question 3

elements ON

Answer 3

0

Question 4

Group 1 metal ON

Answer 4

+1

Question 5

group 2 metals ON

Answer 5

+2

Question 6

Aluminium ON

Answer 6

+3

Question 7

H ON

Answer 7

+1
EXCEPT IN METAL HYDRIDES IT BECOMES -1

Question 8

F ON is alllllways

Answer 8

-1

Question 9

O ON

Answer 9

-2

Question 10

Peroxide ON

Answer 10

O2 (2-)
fluroine takes precedent

Question 11

Cl,Br,I ON

Answer 11

-1
except when with oxygen and fluorine

Question 12

oxidising agent is …

Answer 12

• ELECTRON ACCEPTOR
• species causing another element to oxidise
• it is reduced itself

Question 13

reducing agent…

Answer 13

• ELECTRON DONOR
• species causing another element to be reduced
• it is oxidised itself

Question 14

redox reaction

Answer 14

reaction where both oxidation and reduction occurs

Question 15

disproportionation

Answer 15

an element in a SINGLE SPECIES simultaneously oxidises and reduces

Question 16

in acidic conditions (balancing redox)

Answer 16

• h2o for oxygrn
• add h+ for hydrogen

Question 17

in basic conditions (balancing redox)

Answer 17

DO AS IF ACIDIC (h2o then h+)
- add the same OH as h+ to BOTH SIDES
- cancel

Question 18

superoxide

Answer 18

(o2)-

Question 19

what is combined in redox titrations

Answer 19

reducing agent and oxidising agent

Question 20

manganate 7 ion

Answer 20

MnO4-

Question 21

potassium manganate titrations

Answer 21

• mno4 - to mn2+ (reduced)
• fe 2+ to fe3+ (oxidised)
• must add acid to the iron

Question 22

which acid to use for potassium manganate titration and why

Answer 22

• dilute sulfuric acid
• doesnt oxidise under these conditoins, doesnt react with manganate (7) ions

Question 23

why not use HCl for manganate titrations

Answer 23

can be oxidised to chlorine by the manganate (7) ions

Question 24

why not use HNO3 for manganate titrations

Answer 24

may oxidise the substance

Question 25

why not use ethanoic acid for manganate titrations

Answer 25

too weak

Question 26

why not use CONC sulfuric acid for manganate titrations

Answer 26

may oxidise the substance

Question 27

indicator for potassium manganate titrations

Answer 27

-mno4 2- is purple
- mn2+ is colourless

Question 28

iodine thiosulphate titration

Answer 28

• XS potassium iodide added to oxidising agent
• brown iodine formed
• iodine is titrated with sodium thiosulphate, which oxidises it back to colourless iodide ions
• STARCH INDICATOR IS ADDED WHEN PALE YELLOW, GOES BLUEBLACK TO COLOURLESS