Chapter 7 Electrochemistry ✓

Question 1

What are galvanic cells?

Answer 1

An electrochemical cell that converts the chemical energy of spontaneous redox reactions into electrical energy

Question 2

What do galvanic cells use to produce a voltage?

Answer 2

A redox reaction

Question 3

What is the main function of a galvanic cell?

Answer 3

To convert chemical energy from a redox reaction into electrical energy

Question 4

Why don’t the oxidising and reducing agents in a galvanic cell react directly?

Answer 4

To prevent uncontrolled energy release and allow controlled electron flow through an external circuit

Question 5

What does a salt bridge allow?

Answer 5

It allows ions to move between the oxidising and reducing agent.
If the external circuit is disconnected the redox reaction in the cell stops

Question 6

What are the two types of electrodes?

Answer 6

Cathode and anode

Question 7

What is the cathode in a galvanic cell?

Answer 7

The electrode where reduction takes place

Question 8

What is the anode in a galvanic cell?

Answer 8

The electrode where oxidation takes place

Question 9

How can a redox reaction occur?

Answer 9

-When a conductor joins the two electrodes, as it is the conductor that provides a pathway for electrons to flow from the reducing agent to the oxidising agent.
-In this way the reaction can take place without the reagents making physical contact

Question 10

What is a salt bridge?

Answer 10

A structure in a galvanic cell that allows both positive and negative ions to move between the electrodes, completing the circuit and enabling the cell to produce and electric current

Question 11

Why is ion movement between the oxidising and reducing agents essential in a galvanic cell?

Answer 11

To maintain electrical neutrality by preventing charge build-up on the electrodes.
Without this ion flow, the continuous movement of electrons to the cathode would create an imbalance, and the cell would stop functioning.

Question 12

Draw a galvanic cell with the solutions copper sulfate (Cu2+) and zinc metal (Zn)
optional: Write the half-equations

Answer 12

Question 13

What is an electrolyte?

Answer 13

A substance that dissolves in water to produce a solution that conducts electricity

Question 14

What is the oxidation half-cell?

Answer 14

The part of the cell where oxidation occurs. It consists of the anode plus the surrounding electrolyte

Question 15

What is the reduction half-cell?

Answer 15

The part of the cell where reduction occurs. It consists of the cathode plus the surrounding electrolyte

Question 16

What is the driving force of a redox reaction in a galvanic cell?

Answer 16

Refers to the tendency of electrons to move from the anode (where oxidation occurs) to the cathode (where reduction occurs)

Question 17

What does the driving force of a galvanic cell reflect?

Answer 17

It reflects the combined strength of the oxidising and reducing agents involved

Question 18

What does the voltage produced by a galvanic cell measure?

Answer 18

The driving force of the redox reaction occurring in the cell.

Driving force refers to the tendency of electrons to move from the anode (where oxidation occurs) to the cathode (where reduction occurs)

Question 19

How do you know if a galvanic cell has a high or low driving force

Answer 19

By checking the standard cell potential (E°cell).
-A high, positive E°cell means a strong driving force.
A smaller, negative E°cell means a weaker driving force

Question 20

What does a high positive cell potential mean?

Answer 20

It means the redox reaction is:
-Highly spontaneous (natural)
-Produces more electrical energy
-Pushes electrons strongly through the circuit
-Can do more electrical work

Question 21

What does a small negative cell potential mean?

Answer 21

It means the redox reaction is:
-Non-spontaneous (not natural) but only slightly
-Reaction is close to equilibrium
-Has a weak driving force in the forward direction

Question 22

What does it mean if a redox reaction is spontaneous or not?

Answer 22

-A spontaneous redox reaction happens naturally and produces energy (positive cell potential).
-A non-spontaneous reaction dose not happen on its own and requires energy input (negative cell potential)

Question 23

What reflects the combined strength of the oxidising and reducing agents involved in a galvanic cell?

Answer 23

The cell potential (E°cell) reflects their combined strength
-A higher positive value means stronger oxidising and reducing agents driving the reaction
-A low or negative value means weak agents.

Question 24

What does it mean if an oxidising or reducing agent is strong or weak?

Answer 24

-It refers to how easily it gains or loses electrons.
-A strong oxidising agent (has a high E° value) (e.g. F2) readily gains electrons
-A strong reducing agent (has a low E° value) (e.g. Li) readily loses electrons

Question 25

What is standard reduction potential data?

Answer 25

It is a measure of a substance's ability to be reduced, obtained by comparing it to the hydrogen half-cell under standard conditions

Question 26

What is the reference substance used to measure standard reduction potential?

Answer 26

Hydrogen gas paired with its oxidation product of hydrogen ion is used as the standard and is assigned a potential of exactly 0.00V

Question 27

What are the standard conditions for measuring standard reduction potentials?

Answer 27

25°C 1.0 molL-1 solutions 100kPa pressure for gases

Question 28

What is the standard cell potential?

Answer 28

It is the voltage produced by the galvanic cell under standard conditions due to both oxidation and reduction reactions

Question 29

What does the right half-cell of a standard galvanic cell contain when measuring standard reduction potential?

Answer 29

It contains the test substance and its reduction product

Question 30

Where is hydrogen placed in a standard galvanic cell setup?

Answer 30

In the left half-cell with hydrogen gas and hydrogen ions, to act as the reference for measuring the other substance's reduction potential

Question 31

Draw a standard hydrogen half-cell and a copper half cell

Answer 31

Question 32

Just to remember -The higher the volts the higher the tendency for it to occur and the higher the oxidising agent strength BUT the weaker the reducing agent strength -The lower the volts, the lower the tendency for it to occur and the lower the oxidising agent strength BUT the higher the reducing agent strength

Question 33

How to calculate the E°cell

Answer 33

E°reduction + E°oxidation

Question 34

What does a positive and negative value of E°cell say about the reaction being spontaneous or not?

Answer 34

-A positive value means the redox reaction will actually take place (spontaneous) -A negative value means the redox reaction will not occur (non-spontaneous); instead it would occur spontaneously in the reverse direction

Question 35

What is electrolysis?

Answer 35

A process where electrical energy is used to drive a non-spontaneous redox reaction

Question 36

What is a electrolysis cell?

Answer 36

It is a setup with two electrodes and a power supply that uses electricity to force a chemical reaction to happen

Question 37

What are the components of an electrolytic cell?

Answer 37

-DC power supply -Anode -Cathode -Electrolyte DC power supply -Pushes electrons from the power supply to the cathode (-) and pulls electrons away from the anode (+). This gives the energy needed for the reaction Anode (+): Where oxidation happens, It gives away electrons and is connected to the positive side of the power side Cathode (-): Where reduction happens. It receives electrons and is connected to the negative side of the power supply Electrolyte -A molten or dissolved ionic substance -Anions (-) go to the anode (+) -Cations (+) go to the cathode (-)

Question 38

Draw an electrolysis cell showing the electrolysis of molten sodium chloride using inert platinum electrodes

Answer 38

Question 39

What type of electrodes are used in the electrolysis of a molten salt?

Answer 39

Inert electrodes (a type of electrode which does not participate in a chemical reaction) (e.g. platinum) are used in molten salt electrolysis

Question 40

What is molten salt electrolysis?

Answer 40

The process of using electricity to break down molten (melted) ionic compounds into its elements

Question 41

What do cation and anions do during molten salt electrolysis?

Answer 41

-Cations move to the negative electrode (cathode) and gain electrons (reduction) -Anions move to the positive electrode (anode) and lose electrons (oxidation)

Question 42

What happens when a DC voltage is applied to the electrodes in molten salt electrolysis?

Answer 42

The electrode becomes oppositely charged, causing ions to move and redox reaction to occur.

Question 43

Why is predicting reactions in aqueous electrolysis more complex?

Answer 43

Because in aqueous solutions, water and some electrode materials can also undergo oxidation or reduction. This means they can compete with the salt ions for reaction, making it harder to predict which species will actually react at each electrode

Question 44

What happens if water is oxidise during aqueous electrolysis?

Answer 44

A colourless gas (O2) forms at the anode and the pH near the anode decreases

Question 45

What happens if water is reduced during aqueous electrolysis?

Answer 45

A colourless gas (H2)forms at the cathode and the pH near the cathode increases

Question 46

What happens if the metallic electrode is oxidised in aqueous electrolysis?

Answer 46

The metal anode dissolved and loses mass.