Electrochemistry

Question 1

Define a redox reaction

Answer 1

reaction involving the transfer of electron

Question 2

Oxidation

Answer 2

loss of electrons

Question 3

reduction

Answer 3

gain of electrons

Question 4

Oxidizing agent

Answer 4

substance that accepts electron

Question 5

reducing agent

Answer 5

substance that donates electrons

Question 6

Anode

Answer 6

electrode where oxidation occurs

Question 7

Cathode

Answer 7

electrode where reduction occurs

Question 8

Define Electrolyte

Answer 8

a substance that can conduct electricity by forming free ions when dissolved in a solution

Question 9

Describe the galvanic cell

Answer 9

galvanic cell reaction is spontaneous, exothermic reaction which converts chemical energy to electrical energy

Question 10

What is the structure of the galvanic cell

Answer 10

1- two half cells
2- an anode (the negative half cell where oxidation occurs)
3- cathode (positive half cell where reduction occurs)
4- electrolyte in each half cell which contains ions of the oxidizing and reducing agents
5- an electrode in each half cell
6- salt bridge connecting the two half cells

Question 11

What is the purpose of a salt bridge

Answer 11

1- maintains electrical neutrality
2- completes the circuit

Question 12

What happens at the anode half cell

Answer 12

at the anode half cell it undergoes oxidation which increases the number of positive ions in the electrolyte solution

Question 13

What happens at the Cathode half cell

Answer 13

undergoes reduction, decreases the concentration of postive ions

Question 14

What does the salt bridge do

Answer 14

to maintain electrical neutrality, positive ions from the salt bridge move into the cathode half and negative ions into the anode half cell

Question 15

What are the Standard conditions

Answer 15

1- temp= 25
2-concentration of the electroltye =1mol.dm-3 (aq)
3- pressure =1 atm (only gases)

Question 16

Why is the Pt used as an electron

Answer 16

conduct electricty
it is solid
it is inert

Question 17

Describe the standard hydrogen electrode and explain its role as the reference electrode

Answer 17

All electrode potentials are measured relative to the standard hygrogen electrode which is defined electrode potential of 0.00v
the conditions
temp= 25
concentration of hydronium ions= 1mol.dm-3
pressure of h2 gas is 1 atm
contains a pt electrode

Question 18

How will an increase in concentration of electrolyte effect the initial emf

Answer 18

and increase causes stress to the system and according to le chateliers principle the system will react to decrease the concentration of the electrolye therefore reverse is favoured (decrease concentration of products) which uses up all the ions therefore, the initial emf will decreases

Question 19

how will and increse in the pressure of electrode effect the initial emf of the cell

Answer 19

pressure causes stress to the system according to le chateliers principle the system will react to decrease the pressure the forward reaction is favored which produces fewer moles of gas which will increase the initial emf

Question 20

how does the size of the salt bridge effect the cells ability to deliver current

Answer 20

A shorter, wider salt bridge lowers the internal resistance and increases the cells ability to deliver current
A longer thinner salt bridge increases the internal resistance