Redox processes

Question 1

The oxidation state of all elements is

Answer 1

zero

Question 2

The sum of the oxidation states in a molecule/ion =

Answer 2

the charge of the molecule/ion

Question 3

Oxygen in a compound has an oxidation state of

Answer 3

-2

Question 4

Hydrogen in a compound has an oxidation state of ___ *Except if it is bonded to a metal, when the charge is ___

Answer 4

+1, -1

Question 5

Fluorine in a compound has an oxidation state of

Answer 5

-1

Question 6

Oxidation state of metals in a compound =

Answer 6

+(valence electrons)

Question 7

Halogens are probably __, but can be flexible

Answer 7

-1

Question 8

adding oxygen is (oxidation/reduction)

Answer 8

oxidation

Question 9

removing oxygen is (oxidation/reduction)

Answer 9

reduction

Question 10

Removing hydrogen is (oxidation/reduction)

Answer 10

oxidation

Question 11

Adding hydrogen is (oxidation/reduction)

Answer 11

reduction

Question 12

Loss of electrons is (oxidation/reduction)

Answer 12

oxidation

Question 13

Gain of electrons is (oxidation/reduction)

Answer 13

reduction

Question 14

Increase in oxidation state is (oxidation/reduction)

Answer 14

oxidation

Question 15

Decrease in oxidation state is (oxidation/reduction)

Answer 15

reduction

Question 16

an oxidising agent is

Answer 16

itself reduced

Question 17

Deduce redox equations using half equations:

Answer 17

Split into obvious half equations
Balance electrons (they should be on opposite sides of the two equations)

Question 18

Balancing half equations in acidic solution:

Answer 18

Split into two half equations
Balance anything obvious
add :
H2O
H+
E-
Multiply half equations so that the number of electrons are equal
Combine and cancel

Question 19

In a redox equation, the most reactive element ends up as

Answer 19

an ion

Question 20

In a voltaic cell, The negative electrode (the one higher up the reactivity series) ___ and the positive electrode ____

Answer 20

oxidises, reduces

Question 21

Difference between an electrolytic cell and a voltaic cell

Answer 21

Electrolytic cell - uses electricity to convert electrical energy to chemical energy
Voltaic cell - makes electricity, chemical energy to electrical energy

Question 22

What are salt bridges usually made out of and why?

Answer 22

NaNO3 because it’s very unreactive

Question 23

What is the purpose of the salt bridge?

Answer 23

Completes the circuit

Balances the charge in the half cells

Question 24

in a voltaic cell, which is the anode and which is the cathode?

Answer 24

anode - negative

cathode - positive

Question 25

in an electrolytic cell, which is the anode and which is the cathode?

Answer 25

anode - positive

cathode - negative

Question 26

What is the purpose of wires in an electrolytic cell?

Answer 26

Wires conduct the electricity and are unchanged

Question 27

What is an electrolyte -

Answer 27

a substance that conducts electricity as a liquid and is chemically decomposed in the process. As a solid, it is an insulator

Question 28

What are electrodes usually made of in electrolytic cells?

Answer 28

graphite or platinum, both of which are unreactive

Question 29

Which direction do the electrons move?

Answer 29

Towards the cathode

Question 30

What are the charge carriers in an electrolytic cell?

Answer 30

In the wires, electrons

In the electrolytes, ions