9.1 Oxidation and reduction

Question 1

what is the current definition of oxidation?

Answer 1

loss of electrons

Question 2

what is the current definition of reduction?

Answer 2

gain of electrons

Question 3

what are the 2 old definitions of oxidation?

Answer 3

1. addition of oxygen
2. loss of hydrogen

Question 4

what are the 2 old definitions of reduction?

Answer 4

1. loss of oxygen
2. gain of hydrogen

Question 5

why are the old definitions insufficent?

Answer 5

not every compound that is oxidized adds or loses oxygen or hydrogen

Question 6

what is the mnemonic for the definitions of oxidation and reduction?

Answer 6

OILRIG
oxidation is the loss of electrons
reduction is the gain of electrons

Question 7

how is oxidation related to oxidation state?

Answer 7

oxidation causes a gain in oxidation state

Question 8

How is reduction related to oxidation state?

Answer 8

reduction causes a reduction/ decrease in oxidation state

Question 9

what is a redox reaction?

Answer 9

a reduction and oxidation reaction, as both occurs at the same time

Question 10

what are the 5 steps of the Winkler method?

Answer 10

1. saturate water with oxygen
2. leave for 5 days
3. add excess manganese (II) salt
4. add potassium iodide
5. titrate with sodium thiosulphate

Question 11

how many moles of dissolved oxygen are found using the Winkler method?

Answer 11

1/4 moles of produced iodine or used thiosulphate

Question 12

what is the conversion of ppm to SI units?

Answer 12

1 ppm = 1 mg/dm^3

Question 13

what is the formula for the concentration of oxygen in ppm?

Answer 13

[O2} = mass of oxygen (g)/ volume of oxygen (cm3) x 10^6

Question 14

what is the formula for BOD?

Answer 14

BOD = final [O2] - initial [O2]

Question 15

what is the difference between oxidation and reduction?

Answer 15

oxidation is the loss of electrons and reduction is the gain of electrons

Question 16

why does oxidation and reduction occur at the same time during a reaction?

Answer 16

if a substance is oxidized, it means that the other substance is reduced. therefore, they always occur at the same time

Question 17

—- is an increase in oxidation state

Answer 17

oxidation

Question 18

—- is a decrease in oxidation state

Answer 18

reduction

Question 19

an —- is a substance that oxidizes another substance and itself undergoes reduction

Answer 19

oxidizing agent

Question 20

a —- is a substance that reduced another substance and itself undergoes oxidation

Answer 20

reducing agent

Question 21

the —- is the application of redox to measure the biological oxygen demand

Answer 21

winkler method

Question 22

the amount of dissolved oxygen required to decompose organic material in water is called the —-

Answer 22

biological oxygen demand (BOD)

Question 23

1 mole of produced iodine or used thiosulphate in the winkler method is equal to —-

Answer 23

4 times the moles of dissolved oxygen

Question 24

the —- is a table outlining the order of how easily different elements undergo oxidation, which decreases down the list

Answer 24

reactivity series