Redox

Question 1

oxidation

Answer 1

increase in oxidation number gain of oxygen loss of hydrogren loss of electrons

Question 2

reduction

Answer 2

decrease in oxidation number loss of oxygen gain of hydrogen gain of electrons

Question 3

redox reaction

Answer 3

one in which there are changes in oxidation number

Question 4

oxidising agent

Answer 4

oxidises another species reduced itself takes electrons

Question 5

reducing agent

Answer 5

reduces another species oxidised itself forces its electrons onto other species

Question 6

oxidation state/number

Answer 6

made up construct treats every element as if it was ion

Question 7

elements always

Answer 7

0

Question 8

compounds add up to

Answer 8

0

Question 9

polyatomic ions add up to

Answer 9

charge

Question 10

simple ions

Answer 10

oxidation number = charge

Question 11

group 1, 2, 13

Answer 11

always +1, +2, +3

Question 12

fluorine always

Answer 12

-1

Question 13

hydrogen almost always

Answer 13

+1

Question 14

oxygen almost always

Answer 14

-2

Question 15

chlorine usually

Answer 15

-1

Question 16

oxidation number of F in F2

Answer 16

0

Question 17

reactivity

Answer 17

how easily something reacts

Question 18

best metallic oxidising agent

Answer 18

less reactive bc easier to gain electrons

Question 19

best metallic reducing agent

Answer 19

more reactive bc easier to lose electrons

Question 20

how does a voltaic cell work?

Answer 20

chemical reaction generates electricity

Question 21

electrolysis

Answer 21

electric current drives reactions of oxidation and reduction - stalbe compounds are broken down into their elements

Question 22

reactivity series

Answer 22

list of relative strengths of metals as reducing agents

Question 23

what will more reactive metals do in redox reaction equations?

Answer 23

go from atoms to ions

Question 24

disproportionation

Answer 24

reactions in which the same element is simultaneously oxidised and reduced

Question 25

why is the dissolved oxygen content of water the most important indicators of water quality?

Answer 25

as the level of pollution in water increases, the dissolved oxygen content generally decreases

Question 26

biological oxygen demand (BOD)

Answer 26

amount of oxygen used to decompose the organic matter in a sample of water over a specified time period

Question 27

high BOD

Answer 27

indicates greater quantity of degradable organic waste in the water

Question 28

voltaic cell diagram and explanation

Answer 28

Question 29

cell diagram convention

Answer 29

Question 30

saltbridge

Answer 30

• strip or glass tube containing aqueous solution of ions
• movement of ions neutralizes any build up of charge and maintains potential difference
• anions in salt bridge from from cathode to anode (opposes flow of electrons in exernal circuit)
• KNO₃
• ions do not interfere with reactions at electrodes
• without saltbridge, no voltage is generated

Question 31

electrolyic cell

Answer 31

uses an external source of electrical energy to bring about a reox reaction that would otherwise be non-spontaneous

Question 32

electrolyte

Answer 32

molten ionic compound

Question 33

electrodes

Answer 33

• redox reactions occur here
• electrodes remove charge on ions leaving electrically neutral products

Question 34

electrolyic cell diagram and explanation

Answer 34

• electrodes made from conducting substance and connected to power supply
• inert because do not take part in redox reaction
• electrodes cannot touch