Electrode Potentials

Question 1

What is MnO4- oxidised to

Answer 1

Mn2+

Question 2

What is Cr2O7 2- oxidised to

Answer 2

2Cr 3+

Question 3

What is electrode potential

Answer 3

The potential difference between 2 half cells that make up a cell

Question 4

How is an electrochemical cell produced

Answer 4

When 2 half equations are joined together

Question 5

What side is the negative electrode always on

Answer 5

The left

Question 6

Which equation is flipped and why

Answer 6

The negative one
Because they are always written as reduction equations
The negative one is oxidised

Question 7

What is the equation for calculating emf

Answer 7

Epos- Eneg

Question 8

What does a salt bridge do

Answer 8

Allows the transfer of ions between the cells in order to balance the charge

Question 9

What salt can the salt bridge be filled with an what is a condition of it

Answer 9

Must be inert

Saturated Potassium nitrate or sodium chloride solution

Question 10

Why is a high resistance voltmeter used to measure voltage

Answer 10

Prevents electrons from marvelling continuously form one half cell to another which keeps current low therefore safer

Question 11

What is the reference electrode

Answer 11

The standard hydrogen electrode

Question 12

What side is the standard hydrogen electrode always on

Answer 12

Left side

Question 13

Draw a standard hydrogen electrode

Answer 13

Photo

Question 14

What is the condition for measuring standard hydrogen potentials (2)

Answer 14

All ages at 100kpa
All solutions with conc 1.00 mol dm-3

Question 15

Why platinum used as an electrode in cells with no metal (3)

Answer 15

Good electrical conductor
Inert
Doesn’t react with electrolyte

Question 16

Which ones are the best reducing agents

Answer 16

Most negative

Question 17

Which are the best oxidising agenrs

Answer 17

Most positive

Question 18

To oxidise does the e value have gone higher or lower

Answer 18

Lower / more negative

Question 19

To reduce does the e value have to be higher or lower

Answer 19

Higher / more positive

Question 20

In half equations which ones are you here oxidising and reducing agents

Answer 20

The ones in the right are reducing agents

The ones on the left are oxidising agents

Question 21

What happens to e cell value of concentration of reactants are increased

Answer 21

Equilibrium will shift to the right and e value of half cell increases

Question 22

What happens to e cell value if concentration of products is increased

Answer 22

Equilibrium shifts to the left and e cell value for the half cell decreases

Question 23

What are the2 types of cell

Answer 23

Chargeable - primary cells - only used once

Rechargeable - secondary cells - can be recharged and reused

Question 24

What is the lithium ion cell used in

Answer 24

Mobile phones and laptops

Question 25

What is the anode and cathode of a lithium ion cell

Answer 25

Lithium cobalt oxide Carbon graphite Refer to photo

Question 26

What are the half equations in a lithium ion cell

Answer 26

Photo

Question 27

How are cells rechargeable

Answer 27

By reversing the cell reactions by applying an external voltage to drive electrons in the opposite directions

Question 28

What type of system is a fuel cell

Answer 28

An open system - the reactants flow in and out rather than being stored

Question 29

What do commercial hydrogen oxygen cells used and why

Answer 29

Porous platinum electrodes in contact with concentrated KOH to increase surface area

Question 30

Why can hydrogen fuel cells be polluting

Answer 30

Processed used or produce the hydrogen for example electricity for electrolysis by fossil fuel power stations And carbon dioxide from reaction if hydrocarbons with steam