Chapter 23 - Redox And Electrode Potentials

Question 1

Define redox

Answer 1

A reaction in which both reduction and oxidation take place.

Question 2

Define oxidation

Answer 2

The loss of electrons or an increase in oxidation number.

Question 3

Define reduction

Answer 3

The gain of electrons or a decrease in oxidation number.

Question 4

what is an oxidising agent?

Answer 4

The oxidising agent:

1) takes electrons away from the atom that is oxidised
2) contains the atom that is reduced

Question 5

what is a reducing agent?

Answer 5

a reducing agent:

1) adds electrons to the atom that is reduced
2) is itself oxidised

Question 6

What is the Manganate half reaction?

Answer 6

Question 7

how can redox reactions be written from oxidation numbers?

Answer 7

increase in oxidation number = decrease in oxidation number for another atom

Question 8

What is the iodine + sodium thiosulphate reaction?

Answer 8

Question 9

Why is there no clear colour change at the end point of a Vanadium and Potassium Manganate titration?

Answer 9

KMnO(4) is purple/pink

V2+ is violet

Question 10

What property does the voltmeter have in a cell?

Answer 10

High resistance

Question 11

Which way does the current flow in the cell?

Answer 11

Negative electrode to the positive electrode

Question 12

How do the ions flow between cells?

Answer 12

ions flow across the Salt bridge

Question 13

What is the salt bridge generally made of?

Answer 13

Potassium nitrate (KNO3)
Ammonium nitrate (NH4NO3)

Question 14

What is the electrode made of in a standard hydrogen cell?

Answer 14

Platinum

Question 15

What is in the half cell of Fe3+ and Fe2+?

Answer 15

Inert Pt electrode and Equimolar Fe2+ and Fe3+ (1 mol dm^-3)

Question 16

When two half cells are connected, which is oxidised and which is reduced?

Answer 16

More reactive metal is oxidised

Less reactive metal is reduced

Question 17

Define standard electrode potential

Answer 17

The emf of a half cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1 mol/dm^3 and a gas pressure of 100kPa.

Question 18

What is the electrode potential of a hydrogen half cell?

Answer 18

0.00V

Question 19

What is the electrode potential of the cell?

Answer 19

Electrode potential of the positive terminal minus the electrode potential of the negative terminal

Question 20

How do we know if a cell is feasible?

Answer 20

If the electrode potential of the cell is positive, the reaction is feasible.

Question 21

what’s the Eo of a cell equation?

Answer 21

Eo cell = Eo (positive electrode) - Eo (negative electrode)

Question 22

what are metal/metal ion half cells?

Answer 22

the half cell is a metal rod dipped in a solution of its metal ion

Question 23

what is an ion/ion half cell?

Answer 23

An ion/ion half cell is a solution containing ions of the same element in different oxidation states

Question 24

what is electrode potential?

Answer 24

electrode potential, E, is the tendency for electrons to be gained and for reduction to take place in a half cell

Question 25

how do you measure a standard electrode potential?

Answer 25

To measure electrode potential, the half cell is connected to a standard hydrogen potential.

1) the electrodes are connected by a wire to allow a controlled flow of electrons through a voltmeter
2) The two solutions are connected by a salt bridge
3) The salt bridge contains ions

Question 26

what does the more negative the Eo value mean?

Answer 26

The more negative the Eo value

1) it’s more likely to lose electrons and undergo oxidation
2) the less the tendency to gain electrons and undergo reduction