5.2.3 Redox and electrode potentials

Question 1

What are the oxidation states order of priority?

Answer 1

Group 1,2 and 3
Fluorine
Hydrogen
Oxygen
Chlorine

Question 2

What happens to the oxidation state during oxidation?

Answer 2

Increases the oxidation state

Question 3

What happens to the oxidation state during reduction?

Answer 3

Decreases the oxidation state

Question 4

What is an oxidising agent?

Answer 4

Takes electrons from what is oxidised

Question 5

What is a reducing agent?

Answer 5

Gives electrons to what is reduced

Question 6

What are the steps for balancing redox half equations?

Answer 6

1. Oxidation states
2. Add electrons
3. H+ number to balance charges
4. Add waters to balance equation - no. of oxygens or half the number of hydrogens

Question 7

What do you do when combining half equations?

Answer 7

Balance equations so they have the same number of electrons, cancel out electrons and combine the 2 equations together

Question 8

What are the 2 metals dipped in the solutions of the metal ions called?

Answer 8

Electrodes

Question 9

What will happen at each electrode?

Answer 9

2 reactions will occur, there will be oxidation at one electrode and reduction at the other electrode

Question 10

What creates the voltage in an electrochemical cell?

Answer 10

Electrons flowing through the wire

Question 11

Are the oxidation and reduction reactions at the electrodes reversible?

Answer 11

YES

Question 12

What is the definition of standard electrode potential?

Answer 12

The emf (voltage) of a half cell compared with a standard hydrogen electrode at standard conditions of 298K, conc 1.0M and 1atm pressure

Question 13

What happens at the electrode with the most positive standard electrode potential?

Answer 13

Reduction occurs (gain of electrons)

Question 14

What happens at the electrode with the most negative standard electrode potential?

Answer 14

Oxidation occurs (loss of electrons)

Question 15

If the standard electrode potential is more positive what happens?

Answer 15

Gain electrons

Question 16

If the standard electrode potential is more negative what happens?

Answer 16

Lose electrons

Question 17

What is the equation to calculate the electrode potential of a cell?

Answer 17

Electrode potential of most positive - electrode potential of most negative

Question 18

What does the electrode potential need to be in order for the reaction to be regarded as feasible?

Answer 18

Generally positive

Question 19

What are electrochemical cells used for?

Answer 19

As sources of electrical energy, can be non rechargeable, rechargeable and fuel cells

Question 20

What is a fuel cell?

Answer 20

A device that converts chemical energy into electrical energy by the reaction of a fuel with oxygen to create a voltage

Question 21

What are uses of fuel cells?

Answer 21

In stationary systems e.g. submarines

Question 22

What are advantages of hydrogen fuel cells?

Answer 22

Constant voltage

Less CO2 pollution

Greater efficiency

Question 23

What are disadvantages of hydrogen fuel cells?

Answer 23

Limited life span

Hydrogen is flammable

Toxic chemicals used in production

Question 24

Disadvantages of galvanic cells (batteries)?

Answer 24

Batteries will need to be replaced or recharged

Less efficient

Lots of earths resources needed

Toxic chemicals used in lithium batteries

Risk of fires from lithium batteries