redox reactions

Question 1

what is oxidation?

Answer 1

add O2, remove H2, lose e, increase oxidation state

Question 2

what is reduction?

Answer 2

remove O2, add H2, gain e, decrease oxidation state

Question 3

what is an oxidising agent?

Answer 3

causes oxidation of another substance

itself is reduced

Question 4

what is a reducing agent?

Answer 4

causes reduction of another substance

itself is oxidised

Question 5

define disproportionation reaction

Answer 5

a redox reaction in which the same element is simultaneously reduced and oxidised to form 2 different products

Question 6

define comproportionation reaction

Answer 6

a redox reaction in which 2 reactants, each containing the same element but with different oxidation states, will form a product in which the element involved reaches the same oxidation state

Question 7

MnO4- as oxidising agent:

Answer 7

acidic medium: purple -> colourless
acidified with H2SO4

not acidified with HCl cuz Cl ions will be oxidised by MnO4-
not acidified with HNO3 cuz it is a strong oxidising agent and may interfere with the oxidising action of MnO4-

Question 8

Cr2O7- as oxidising agent:

Answer 8

orange -> green
acidified with H2SO4

Question 9

S2O3 2- as reducing agent:

Answer 9

dark blue -> colourless(when all I- is reacted)
indicator used: starch (to give a more distinct colour change)

usually reacted with iodine in a titration