Electrochemistry

Question 1

What is the electrolyte?

Answer 1

The electrolyte is the ionic compound in molten or dissolved solution that conducts the electricity.

Question 2

What is the anode?

Answer 2

The anode is the positive electrode.

Question 3

What is the cathode?

Answer 3

The cathode is the negative electrode.

Question 4

Which way do electrons flow in the circuit during electrolysis?

Answer 4

Electrons flow from the anode to the cathode.

Question 5

Why are cations attracted to the cathode?

Answer 5

Positive cations are attracted to the negatively charged cathode because opposite charges attract.

Question 6

Why are anions attracted to the anode?

Answer 6

Negative anions are attracted to the positively charged anode because opposite charges attract.

Question 7

Define electrolysis

Answer 7

Electrolysis is the process of using an electric current to decompose or break down a molten or aqueous ionic compound.

Question 8

What is produced at the cathode during electrolysis of molten lead(II) bromide?

Answer 8

Molten lead is produced at the cathode during electrolysis of molten lead(II) bromide.

Question 9

What is produced at the anode during electrolysis of molten lead(II) bromide?

Answer 9

Brown fumes of bromine gas are produced at the anode during electrolysis of molten lead(II) bromide.

Question 10

What would be the products of electrolysis of molten zinc chloride?

Answer 10

The products of electrolysis of molten zinc chloride would be zinc at the cathode and chlorine at the anode.

Question 11

What type of electrodes are typically used in the electrolysis of molten compounds?

Answer 11

Graphite or platinum electrodes are typically used in the electrolysis of molten compounds.

Question 12

Why do molten ionic compounds conduct electricity?

Answer 12

Molten ionic compounds conduct electricity because their ions can move freely and carry the current.

Question 13

Explain how a molecule of chlorine forms during the electrolysis of lead(II) chloride.

Answer 13

Two chloride ions are attracted to the anode where they each lose one electron.

They bond to form a molecule of chlorine.

2Cl- ⟶ Cl2 + 2e-

Question 14

What is brine?

Answer 14

Brine is a concentrated solution of aqueous sodium chloride.

Question 15

What are the products of the electrolysis of brine?

Answer 15

The products of the electrolysis of brine are chlorine gas, hydrogen gas, and sodium hydroxide solution

Question 16

What gas is produced at the anode during the electrolysis of brine?

Answer 16

Chlorine gas is produced at the anode during the electrolysis of brine.

Question 17

In the electrolysis of dilute sulfuric acid, what gas is produced at the cathode?

Answer 17

In the electrolysis of dilute sulfuric acid, hydrogen gas is produced at the cathode.

Question 18

What is produced at the anode during the electrolysis of dilute sulfuric acid?

Answer 18

Oxygen gas is produced at the anode during the electrolysis of dilute sulfuric acid.

Question 19

What is the test and result for oxygen gas?

Answer 19

The test for oxygen gas is that a glowing splint will relight when dipped into a sample of the gas.

Question 20

What is the test and result for hydrogen gas?

Answer 20

Hydrogen gas is tested for by dipping a lit splint into a sample of the gas, which will produce a squeaky pop.

Question 21

What is the test and result for chlorine gas?

Answer 21

The test for chlorine gas is that damp litmus paper will turn red and then bleach to a white colour when dipped into a sample of the gas.

Question 22

What ions are always present in aqueous solutions?

Answer 22

Aqueous solutions always have H+ and OH- ions present from the splitting of water molecules.

Question 23

What determines which ions are discharged at the electrodes during electrolysis of aqueous solutions?

Answer 23

The relative reactivity of the elements involved determines which ions are discharged at the electrodes during electrolysis of aqueous solutions.

Question 24

In the electrolysis of concentrated copper(II) chloride solution, what is produced at the anode?

Answer 24

In the electrolysis of concentrated copper(II) chloride solution, chlorine is produced at the anode.

Question 25

What is produced at the anode during the electrolysis of dilute halide solutions?

Answer 25

Oxygen is produced at the anode during the electrolysis of dilute halide solutions.

Question 26

What is produced at the cathode during the electrolysis of aqueous copper sulfate?

Answer 26

Copper metal is produced at the cathode during the electrolysis of aqueous copper sulfate.

Question 27

In the electrolysis of aqueous copper sulfate with copper electrodes, what happens to the anode?

Answer 27

In the electrolysis of aqueous copper sulfate with copper electrodes, the anode decreases in mass.

Question 28

What is produced at the anode during the electrolysis of dilute sulfuric acid?

Answer 28

Oxygen gas is produced at the anode during the electrolysis of dilute sulfuric acid.

Question 29

What ions are attracted to the positive electrode?

Answer 29

Negatively charged OH- ions and non-metal ions are attracted to the positive electrode.

Question 30

What ions are attracted to the negative electrode?

Answer 30

H+ ions and metal ions are attracted to the negative electrode.

Question 31

How is the product at the cathode determined?

Answer 31

The product at the cathode is determined by the position of the metal in the reactivity series relative to hydrogen.

Question 32

What is produced at the cathode during electrolysis of dilute sodium chloride solution?

Answer 32

Hydrogen gas is produced at the cathode during electrolysis of sodium chloride solution.

Question 33

What is oxidation in terms of electron transfer?

Answer 33

Oxidation is the loss of electrons.

Question 34

What is reduction in terms of electron transfer?

Answer 34

Reduction is the gain of electrons.

Question 35

Write the ionic half-equation for the reduction of copper(II) ions

Answer 35

Cu2+ + 2e- → Cu

Question 36

Write the ionic half-equation for the oxidation of chloride ions

Answer 36

2Cl- → Cl2 + 2e-

Question 37

What is the ionic half-equation for the reduction of hydrogen ions?

Answer 37

2H+ + 2e- → H2

Question 38

Write the ionic half- equation for the reduction of Sn2+ ions at the cathode?

Answer 38

Sn2+ + 2e- → Sn

Question 39

State the ionic half- equation for the reduction of Pb2+ ions at the cathode.

Answer 39

Pb2+ + 2e- → Pb

Question 40

What is electroplating?

Answer 40

Electroplating is process of coating the surface of one metal with a layer of a different metal.

Question 41

Give one use of electroplating.

Answer 41

Uses of electroplating include: Improving the appearance of objects (e.g. jewellery) Coating objects to prevent corrosion / damage (e.g. cutlery)

Question 42

An iron nail is being electroplated with copper. Which metal is being used as the anode?

Answer 42

The anode is the copper rod as the anode is the metal you are using the coat the other metal with.

Question 43

What is the ionic half- equation for the reaction at the anode which forms Sn2+ ions when electroplating with tin?

Answer 43

Sn → Sn2+ + 2e-

Question 44

What is the ionic half- equation for the reaction at the cathode forming Sn atoms when electroplating with tin?

Answer 44

Sn2+ + 2e- → Sn

Question 45

A substance is electroplated with tin (Sn) What is the ionic half- equation for the formation of Sn2+ ions at the anode?

Answer 45

Sn → Sn2+ + 2e-

Question 46

A substance is electroplated with tin. What is the ionic half- equation for the formation of Sn atoms at the cathode?

Answer 46

Sn2+ + 2e- → Sn

Question 47

What is a fuel cell?

Answer 47

A fuel cell is an electrochemical cell in which a fuel donates electrons at one electrode and oxygen gains electrons at the other electrode.

Question 48

What are the products of a hydrogen-oxygen fuel cell?

Answer 48

A hydrogen-oxygen fuel cell produces water and energy.

Question 49

Which direction do the electrons flow in a fuel cell?

Answer 49

The electrons flow from anode to cathode.

Question 50

Where is air containing oxygen pumped into a fuel cell?

Answer 50

The air containing oxygen is pumped into the cathode compartment.

Question 51

What is the symbol equation for the reaction between hydrogen and oxygen to form water?

Answer 51

2H2 + O2 → 2H2O

Question 52

State two disadvantages of using fuel cells.

Answer 52

Two disadvantages could be from the following: Materials used in producing fuel cells are expensive Hydrogen is difficult to store as it is flammable

Question 53

State two advantages of using fuel cells

Answer 53

Two advantages could be from the following: The only product is water so less pollution They produce more energy per kilogram than either petrol or diesel