Electrochemical Cell

Question 1

What is the construction and functioning of the Daniell cell?

Answer 1

The Daniell cell converts chemical energy from a redox reaction to electrical energy, with an electrical potential of 1.1 V when Zn²⁺ and Cu²⁺ concentrations are unity (1 mol dm³).

The reaction is represented as Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s).

Question 2

What type of cell is the Daniell cell?

Answer 2

It is a galvanic or voltaic cell.

Galvanic cells convert chemical energy into electrical energy.

Question 3

What happens when an external potential less than 1.1 V is applied to the Daniell cell?

Answer 3

Electrons flow from the Zn rod to the Cu rod, resulting in current flowing from Cu to Zn.

Zn dissolves at the anode and copper deposits at the cathode.

Question 4

What occurs when the external potential is exactly 1.1 V?

Answer 4

No flow of electrons or current occurs, and no chemical reaction takes place.

This is the equilibrium state of the Daniell cell.

Question 5

What happens when the external potential exceeds 1.1 V?

Answer 5

Electrons flow from Cu to Zn, and current flows from Zn to Cu.

Zinc is deposited at the zinc electrode and copper dissolves at the copper electrode.

Question 6

What is the role of the salt bridge in a galvanic cell?

Answer 6

The salt bridge maintains electrical neutrality by allowing the flow of ions between the two half-cells.

It helps to balance the charges as the cell operates.

Question 7

Define an electrolytic cell.

Answer 7

An electrolytic cell is a device that uses electrical energy to drive non-spontaneous chemical reactions.

This occurs when the external voltage applied exceeds the cell’s potential.

Question 8

Fill in the blank: The Daniell cell operates under spontaneous conditions when Eext < _______.

Answer 8

1.1 V

Question 9

True or False: The Daniell cell can function as both a galvanic cell and an electrolytic cell.

Answer 9

True

Question 10

What are the two half-reactions in the Daniell cell?

Answer 10

1. Oxidation: Zn → Zn²⁺ + 2e⁻
2. Reduction: Cu²⁺ + 2e⁻ → Cu

These reactions occur at the anode and cathode, respectively.

Question 11

What is the significance of using activity instead of concentration in electrochemistry?

Answer 11

Activity is directly proportional to concentration and is more accurate in dilute solutions.

In high concentration solutions, activity and concentration may differ significantly.

Question 12

What is a galvanic cell?

Answer 12

An electrochemical cell that converts the chemical energy of a spontaneous redox reaction into electrical energy.

Question 13

What is the overall reaction in a Daniell cell?

Answer 13

Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Question 14

What are the two half reactions in a Daniell cell?

Answer 14

• Cur²⁺ + 2e → Cu(s) (reduction half reaction)
• Zn(s) → Zn²⁺ + 2e (oxidation half reaction)

Question 15

Where does the reduction half reaction occur in a Daniell cell?

Answer 15

On the copper electrode.

Question 16

Where does the oxidation half reaction occur in a Daniell cell?

Answer 16

On the zinc electrode.

Question 17

What are the two portions of a galvanic cell called?

Answer 17

Half-cells or redox couples.

Question 18

What is the role of the salt bridge in a galvanic cell?

Answer 18

Connects the electrolytes of the two half-cells internally.
Maintain electrical neutrality
Prevents mixing of electrolytes

Question 19

What is electrode potential?

Answer 19

The potential difference that develops between the electrode and the electrolyte.

Question 20

What is standard electrode potential?

Answer 20

The electrode potential when the concentrations of all species in a half-cell are unity.

Question 21

What is the anode in a galvanic cell?

Answer 21

The half-cell where oxidation takes place and has a negative potential.

Question 22

What is the cathode in a galvanic cell?

Answer 22

The half-cell where reduction takes place and has a positive potential.

Question 23

True or False: The direction of current flow is the same as the flow of electrons in a galvanic cell.

Answer 23

False.

Question 24

Fill in the blank: In a galvanic cell, electrons flow from the _______ electrode to the _______ electrode.

Answer 24

negative; positive

Question 25

What is a galvanic cell?

Answer 25

An electrochemical cell that converts the chemical energy of a spontaneous redox reaction into electrical energy.

Question 26

What is the overall reaction in a Daniell cell?

Answer 26

Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Question 27

What are the two half reactions in a Daniell cell?

Answer 27

* Cur²⁺ + 2e → Cu(s) (reduction half reaction) * Zn(s) → Zn²⁺ + 2e (oxidation half reaction)

Question 28

Where does the reduction half reaction occur in a Daniell cell?

Answer 28

On the copper electrode.

Question 29

Where does the oxidation half reaction occur in a Daniell cell?

Answer 29

On the zinc electrode.

Question 30

What are the two portions of a galvanic cell called?

Answer 30

Half-cells or redox couples.

Question 31

What is the role of the salt bridge in a galvanic cell?

Answer 31

Connects the electrolytes of the two half-cells internally.

Question 32

What is electrode potential?

Answer 32

The potential difference that develops between the electrode and the electrolyte.

Question 33

What is standard electrode potential?

Answer 33

The electrode potential when the concentrations of all species in a half-cell are unity.

Question 34

What is the anode in a galvanic cell?

Answer 34

The half-cell where oxidation takes place and has a negative potential.

Question 35

What is the cathode in a galvanic cell?

Answer 35

The half-cell where reduction takes place and has a positive potential.

Question 36

True or False: The direction of current flow is the same as the flow of electrons in a galvanic cell.

Answer 36

False.

Question 37

Fill in the blank: In a galvanic cell, electrons flow from the _______ electrode to the _______ electrode.

Answer 37

negative; positive

Question 38

What is standard electrode potential?

Answer 38

The potential difference that develops between electrode and electrolyte electrode potential. When concentration of all species involved is unity, electrode potential is known as standard electrode potential.

Question 39

What is standard reduction potential?

Answer 39

SRP is standard electrode potential according to IUPAC convention

Question 40

What is the potential of cathode and anode with respect to the solution?

Answer 40

Potential of cathode is positive and potential of an anode is negative

Question 41

What is the cell potential in a galvanic cell?

Answer 41

The potential difference between the two electrodes, measured in volts.

Question 42

What is the cell electromotive force (emf)?

Answer 42

The cell potential when no current is drawn through the cell.

Question 43

In the representation of a galvanic cell, where is the anode placed?

Answer 43

On the left.

Question 44

Where is the cathode placed in the representation of a galvanic cell?

Answer 44

On the right.

Question 45

How is a galvanic cell generally represented?

Answer 45

With a vertical line between metal and electrolyte solution and a double vertical line between two electrolytes connected by a salt bridge.

Question 46

What is the formula for calculating the emf of a cell?

Answer 46

E cell = Eright - Eleft.

Question 47

What is the overall cell reaction for the provided example?

Answer 47

Cu(s) + 2Ag*(aq) → Cu?*(aq) + 2 Ag(s).

Question 48

Which electrode acts as the cathode in the example?

Answer 48

Silver electrode.

Question 49

Which electrode acts as the anode in the example?

Answer 49

Copper electrode.

Question 50

How is the cell represented in the example?

Answer 50

Cu(s) | Cu?*(aq) || Ag*(aq) | Ag(s).

Question 51

What does the potential of individual half-cells depend on?

Answer 51

The difference between the two half-cell potentials.

Question 52

What is the standard hydrogen electrode (SHE) assigned as?

Answer 52

A zero potential at all temperatures.

Question 53

What is the representation of the standard hydrogen electrode?

Answer 53

Pt(s) | H2(g) | H+(aq).

Question 54

What conditions are maintained for the standard hydrogen electrode?

Answer 54

* Pressure of hydrogen gas is one bar * Concentration of hydrogen ion is one molar.

Question 55

What is the reaction corresponding to the standard hydrogen electrode?

Answer 55

H+(aq) + e- → 1/2 H2(g).

Question 56

What material is the standard hydrogen electrode coated with?

Answer 56

Platinum black.

Question 57

True or False: The potential of individual half-cells can be directly measured.

Answer 57

False.

Question 58

What is the cell potential in a galvanic cell?

Answer 58

The potential difference between the two electrodes, measured in volts.

Question 59

What is the cell electromotive force (emf)?

Answer 59

The cell potential when no current is drawn through the cell.

Question 60

In the representation of a galvanic cell, where is the anode placed?

Answer 60

On the left.

Question 61

Where is the cathode placed in the representation of a galvanic cell?

Answer 61

On the right.

Question 62

How is a galvanic cell generally represented?

Answer 62

With a vertical line between metal and electrolyte solution and a double vertical line between two electrolytes connected by a salt bridge.

Question 63

What is the formula for calculating the emf of a cell?

Answer 63

E cell = Eright - Eleft.

Question 64

What is the overall cell reaction for the provided example?

Answer 64

Cu(s) + 2Ag*(aq) → Cu?*(aq) + 2 Ag(s).

Question 65

Which electrode acts as the cathode in the example?

Answer 65

Silver electrode.

Question 66

Which electrode acts as the anode in the example?

Answer 66

Copper electrode.

Question 67

How is the cell represented in the example?

Answer 67

Cu(s) | Cu?*(aq) || Ag*(aq) | Ag(s).

Question 68

What does the potential of individual half-cells depend on?

Answer 68

The difference between the two half-cell potentials.

Question 69

What is the standard hydrogen electrode (SHE) assigned as?

Answer 69

A zero potential at all temperatures.

Question 70

What is the representation of the standard hydrogen electrode?

Answer 70

Pt(s) | H2(g) | H+(aq).

Question 71

What conditions are maintained for the standard hydrogen electrode?

Answer 71

* Pressure of hydrogen gas is one bar * Concentration of hydrogen ion is one molar.

Question 72

What is the reaction corresponding to the standard hydrogen electrode?

Answer 72

H+(aq) + e- → 1/2 H2(g).

Question 73

What material is the standard hydrogen electrode coated with?

Answer 73

Platinum black.

Question 74

True or False: The potential of individual half-cells can be directly measured.

Answer 74

False.

Question 75

What is the emf of the cell at 298 K constructed with a standard hydrogen electrode as anode?

Answer 75

The emf gives the reduction potential of the other half-cell.

Question 76

What happens to the cell potential if the concentrations of oxidized and reduced forms are unity?

Answer 76

The cell potential is equal to standard electrode potential, E°R of the given half-cell.

Question 77

What is the relationship between E° and the electrode potentials?

Answer 77

E° = ER - EL

Question 78

What is the standard electrode potential for the standard hydrogen electrode?

Answer 78

Zero.

Question 79

What is the measured emf of the cell with the reaction Cu²⁺ (aq, 1M) + 2e → Cu(s)?

Answer 79

0.34 V.

Question 80

What does a positive value of standard electrode potential indicate about Cu²⁺ ions compared to H⁺ ions?

Answer 80

Cu²⁺ ions get reduced more easily than H⁺ ions.

Question 81

Can hydrogen ions oxidize copper under standard conditions?

Answer 81

No, hydrogen ions cannot oxidize copper.

Question 82

What is the measured emf of the cell with the reaction Zn²⁺ (aq, 1M) + 2e → Zn(s)?

Answer 82

-0.76 V.

Question 83

What does a negative standard electrode potential for zinc indicate?

Answer 83

Hydrogen ions can oxidize zinc.

Question 84

Write the half-reaction for the left electrode in the Daniell cell.

Answer 84

Zn(s) → Zn²⁺ (aq, 1 M) + 2 e.

Question 85

Write the half-reaction for the right electrode in the Daniell cell.

Answer 85

Cu²⁺ (aq, 1 M) + 2 e → Cu(s).

Question 86

What is the overall reaction of the Daniell cell?

Answer 86

Zn(s) + Cu²⁺ (aq) → Zn²⁺ (aq) + Cu(s).

Question 87

Calculate the emf of the Daniell cell using E° values.

Answer 87

1.10 V.

Question 88

What type of electrodes are platinum or gold classified as?

Answer 88

Inert electrodes.

Question 89

What role do inert electrodes play in electrochemical reactions?

Answer 89

They provide surface for oxidation or reduction reactions and conduction of electrons.

Question 90

What is the half-cell reaction for the hydrogen electrode?

Answer 90

H⁺ (aq) + e → ½ H₂(g).

Question 91

What is the half-cell reaction for the bromine electrode?

Answer 91

Br₂(aq) + 2e → 2Br⁻(aq).

Question 92

What is the emf of the cell at 298 K constructed with a standard hydrogen electrode as anode?

Answer 92

The emf gives the reduction potential of the other half-cell.

Question 93

What happens to the cell potential if the concentrations of oxidized and reduced forms are unity?

Answer 93

The cell potential is equal to standard electrode potential, E°R of the given half-cell.

Question 94

What is the relationship between E° and the electrode potentials?

Answer 94

E° = ER - EL

Question 95

What is the standard electrode potential for the standard hydrogen electrode?

Answer 95

Zero.

Question 96

What is the measured emf of the cell with the reaction Cu²⁺ (aq, 1M) + 2e → Cu(s)?

Answer 96

0.34 V.

Question 97

What does a positive value of standard electrode potential indicate about Cu²⁺ ions compared to H⁺ ions?

Answer 97

Cu²⁺ ions get reduced more easily than H⁺ ions.

Question 98

Can hydrogen ions oxidize copper under standard conditions?

Answer 98

No, hydrogen ions cannot oxidize copper.

Question 99

What is the measured emf of the cell with the reaction Zn²⁺ (aq, 1M) + 2e → Zn(s)?

Answer 99

-0.76 V.

Question 100

What does a negative standard electrode potential for zinc indicate?

Answer 100

Hydrogen ions can oxidize zinc.

Question 101

Write the half-reaction for the left electrode in the Daniell cell.

Answer 101

Zn(s) → Zn²⁺ (aq, 1 M) + 2 e.

Question 102

Write the half-reaction for the right electrode in the Daniell cell.

Answer 102

Cu²⁺ (aq, 1 M) + 2 e → Cu(s).

Question 103

What is the overall reaction of the Daniell cell?

Answer 103

Zn(s) + Cu²⁺ (aq) → Zn²⁺ (aq) + Cu(s).

Question 104

Calculate the emf of the Daniell cell using E° values.

Answer 104

1.10 V.

Question 105

What type of electrodes are platinum or gold classified as?

Answer 105

Inert electrodes.

Question 106

What role do inert electrodes play in electrochemical reactions?

Answer 106

They provide surface for oxidation or reduction reactions and conduction of electrons.

Question 107

What is the half-cell reaction for the hydrogen electrode?

Answer 107

H⁺ (aq) + e → ½ H₂(g).

Question 108

What is the half-cell reaction for the bromine electrode?

Answer 108

Br₂(aq) + 2e → 2Br⁻(aq).

Question 109

What is the standard electrode potential (E°) for the standard hydrogen electrode?

Answer 109

E° = 0 V ## Footnote The standard hydrogen electrode is used as a reference in electrochemical measurements.

Question 110

What is the relationship between the emf of a cell and the standard electrode potential of a half-cell?

Answer 110

E° = ER ## Footnote This equation indicates that the cell potential equals the standard electrode potential of the half-cell when concentrations are unity.

Question 111

What is the measured emf of the cell Pt(s) | H₂(g, 1 bar) | H⁺(aq, 1 M) || Cu²⁺(aq, 1 M) | Cu?

Answer 111

0.34 V ## Footnote This value corresponds to the standard electrode potential of the half-cell reaction Cu²⁺(aq, 1M) + 2 e⁻ → Cu(s).

Question 112

What does a positive standard electrode potential indicate about the reduction of Cu²⁺ ions compared to H⁺ ions?

Answer 112

Cu²⁺ ions get reduced more easily than H⁺ ions ## Footnote This suggests that hydrogen ions cannot oxidise copper under standard conditions.

Question 113

What is the measured emf of the cell Pt(s) | H₂(g, 1 bar) | H⁺(aq, 1 M) || Zn²⁺(aq, 1 M) | Zn?

Answer 113

-0.76 V ## Footnote This value corresponds to the standard electrode potential of the half-cell reaction Zn²⁺(aq, 1 M) + 2 e⁻ → Zn(s).

Question 114

What does a negative standard electrode potential indicate about the oxidation of zinc?

Answer 114

Hydrogen ions can oxidise zinc ## Footnote This means that zinc can reduce hydrogen ions.

Question 115

What are the half-reactions for the Daniell cell?

Answer 115

* Left electrode: Zn(s) → Zn²⁺(aq, 1 M) + 2 e⁻ * Right electrode: Cu²⁺(aq, 1 M) + 2 e⁻ → Cu(s) ## Footnote These reactions illustrate the oxidation and reduction processes occurring in the Daniell cell.

Question 116

What is the overall reaction of the Daniell cell?

Answer 116

Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s) ## Footnote This reaction is the sum of the half-reactions for the cell.

Question 117

How is the emf of the Daniell cell calculated?

Answer 117

emf of the cell = E° cell = E°R - E°L ## Footnote In this case, it calculates to 1.10 V.

Question 118

What are inert electrodes and give examples?

Answer 118

Inert electrodes do not participate in the reaction but provide a surface for oxidation or reduction reactions. ## Footnote Examples include platinum and gold.

Question 119

What is the half-cell reaction for the hydrogen electrode?

Answer 119

H⁺(aq) + e⁻ → ½ H₂(g) ## Footnote This reaction occurs at the platinum electrode in the hydrogen electrode half-cell.

Question 120

What is the half-cell reaction for the bromine electrode?

Answer 120

Br₂(aq) + 2 e⁻ → 2 Br⁻(aq) ## Footnote This reaction occurs at the platinum electrode in the bromine electrode half-cell.