Unit 1- Section 11- Electrochemistry + RP8

Question 1

How many half cells does a cell contain?

Answer 1

two

Question 2

In a cell, how are the half cells connected?

Answer 2

by a salt bridge

Question 3

What is a simple half cell composed of?

Answer 3

• a metal (acts an electrode)
• solution of compound (containing the metal)

Question 4

What happens when two half cells are connected in a circuit?

Answer 4

a voltage will be produced

Question 5

why is a voltage formed in a zinc- copper cell?

Answer 5

because the zinc has a higher tendency to oxidise to the Zn2+ ion and release electrons than the copper half cell.

Question 6

Out of copper and zinc, which electrode will the electrons build up on more?

Answer 6

the zinc electrode, it has a higher tendency to oxidise

Question 7

why is a high resistance voltmeter used?

Answer 7

to measure the maximum potential difference

Question 8

describe a Daniell cell

Answer 8

a zinc anode placed in 1moldm-3 zinc sulphate solution

a copper cathode placed in 1moldm-3 copper sulphate solution

Question 9

What is the role of a salt bridge?

Answer 9

it allows ions to move freely, completing the circuit

Question 10

Usually, what is a salt bridge made of?

Answer 10

filter paper, soaked in potassium nitrate

Question 11

What process happens at the cathode?

Answer 11

reduction, the metal ions gain electrons to form solid metal atoms

Question 12

What process happens at the anode?

Answer 12

oxidation, electrons are generated and flow to the cathode

Question 13

Over time, what happens to the mass of the anode and cathode?

Answer 13

the anode (reactant) will get used up, and the cathode will gain mass

Question 14

What is a metal that is commonly used as an electrode, when other metals can’t be used?

Answer 14

platinum, Pt

Question 15

What does I mean in cell representation?

Answer 15

boundary between different phases

Question 16

What does II mean in cell representation?

Answer 16

salt bridge

Question 17

What are two conventional cell representation rules?

Answer 17

-more oxidised species are written closer to the salt bridge (more charged)

• more positive species are written on the right (mostly)

Question 18

What is a comma used for in cell representation?

Answer 18

it is used to sperate the species in the same phase

Question 19

What does SHE stand for?

Answer 19

standard hydrogen electrode

Question 20

What is a SHE used for?

Answer 20

measuring the potential of a half cell

Question 21

Give the conventional cell representation for a SHE

Answer 21

Pt I H2(g) I H+(aq)

Question 22

Give the standard conditions for SHE

Answer 22

298K
100kPa
H+ ion containing solution of 1moldm-3

Question 23

Why is a metal salt bridge not used?

Answer 23

because it would set up its own metal electrode system with the solutions

Question 24

Why are standard conditions needed for SHE?

Answer 24

Standard conditions are needed because the position of the redox equilibrium will change with conditions. (Le Chatelier’s Principle)

Question 25

How can standard electrode potentials be written?

Answer 25

as an electrochemical series

Question 26

What does a more positive EMF value mean?

Answer 26

it will be easier for it to reduce other substances and to act as a reducing agent

Question 27

What does a more negative EMF value mean?

Answer 27

it will be easier for it to oxidise other substances and to act as an oxidising agent

Question 28

What is the EMF equation?

Answer 28

Ecell = Ered - Eox

Question 29

What unit is EMF measured in?

Answer 29

V