Redox I & II

Question 1

What does a half equation show

Answer 1

Shows the gain or loss of electrons and is balanced for atoms and charge

Question 2

What is oxidation

Answer 2

Loss of electrons

Question 3

What is reduction

Answer 3

Gain of electrons

Question 4

What does the oxidation state number represent

Answer 4

represents the number of electrons lost/gained by an atom relative to its elemental/atomic state.

Question 5

Whats an oxidising agent

Answer 5

a species that oxidises other species (by gaining electrons from them)

Question 6

Whats a reducing agent

Answer 6

a species that reduces other species (by losing/giving electrons to them)

Question 7

What does the overall redox equation showing

Answer 7

the species or ions changing oxidation states.

Question 8

What is a half cell / electrode

Answer 8

an equilibrium system consisting of a solid metal in a solution of its own ions.

Question 9

What is electrode potential?

Answer 9

a measure of the equilibrium position for a half-cell / electrode.

Question 10

What is the standard electrode potential

Answer 10

the voltage produced by a half-cell when connected to a standard hydrogen electrode, under standard conditions (298K, 100kPa, all solutions 1 mol dm-3)

Question 11

What is the problem with not having a salt bridge

Answer 11

The circuit of a cell is not complete

Question 12

What is a half cell / electrode

Answer 12

An equilibrium of a metal and its ions
e.g. Cu(s) ⇌ Cu2+(aq) + 2e-

Question 13

What are the standard conditions for a standard electrode potential

Answer 13

100kPa, 298K, 1 mol dm-3

Question 14

Describe a standard hydrogen electrode (4 marks)

Answer 14

Platinum rod allowing the H2 half reaction to take place, the rod being unreactive
H2 gas bubbles form
under standard conditions which are 298K, 100kPa and in this case, 1 M of H+ ions (acid)

Question 15

What happens if we heat up the below reaction and why
Na+ + e- ⇌ Na

Answer 15

equilibrium shifts left
as the forwards reaction is exothermic as we are making bonds and forming attractions
so the system shifts its equilibrium to counteract the change and so it moves in the endothermic direction
this is the backwards reaction

Question 16

What happens if we heat up the below reaction and why
Cr3+ + 3e- ⇌ Cr

Answer 16

equilibrium shifts left
as the forwards reaction is exothermic as we are making bonds and forming attractions
so the system shifts its equilibrium to counteract the change and so it moves in the endothermic direction
this is the backwards reaction

Question 17

How do represent a cell with a magnesium electrode and a silver electrode

Answer 17

Mg(s) I Mg2+(aq) I I Ag+(aq) I Ag(s)

Question 18

What goes on the right side of the shorthand for representing cells and what does this mean

Answer 18

The most positive thing
this means Ecell values will always positive UNLESS its with a hydrogen cell. Then it could be either positive or negative

Question 19

If a iron cell has an E value of -0.44 and a lead cell has an E value of -0.13, what is the
Ecell value

Answer 19

+0.31