4 Electrolysis

Question 1

Define electrolysis

Answer 1

the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current

Question 2

anode

Answer 2

positive electrode

Question 3

cathode

Answer 3

negative electrode

Question 4

electrolyte

Answer 4

the molten or aqueous substance that undergoes electrolysis

Question 5

products formed at the electrodes made during the electrolysis of molten lead(II) bromide

Answer 5

Cathode: the lead forms
Anode: the bromine forms

Question 6

products formed at the electrodes made during the electrolysis of concentrated aqueous sodium chloride

Answer 6

Cathode: hydrogen gas forms
Anode: chlorine gas forms

Question 7

products formed at the electrodes made during the elctrolysis of dilute sulfuric acid

Answer 7

Cathode: hydrogen gas
Anode: oxygen gas forms

Question 8

what’s substance is formed at the cathode?

Answer 8

metals or hydrogen

Question 9

what’s formed at the anode?

Answer 9

non-metals

Question 10

why are metal objects electroplated?

Answer 10

to improve their appearance and resistance to corrosion

Question 11

Electroplating

Answer 11

putting a thin layer of a metal onto a metal object via electrolysis

Question 12

to carry out electroplating: (electrodes and electrolyte)

Answer 12

• the cathode is the object to be plated
• the anode is the plating metal
• the electrolyte contains ions of the plating metal

Question 13

At the cathode which substance will form a product?

Answer 13

The least reactive one

Question 14

At the anode which substance will form a product?

Answer 14

the halide or if theres no halide then oxygen. unless the concentration of the halide is very low.

Question 15

describe the electrolysis of aqueous copper(II) sulfate using inert electrodes

Answer 15

at anode: oxygen gas forms (bubbles form) and the oxygen reacts with carbon eletrode to form carbon dioxide
at cathode: copper forms (accumilating on its exterior)

Question 16

describe the electrolysis of aqueous copper(II) sulfate using copper electrodes

Answer 16

at anode: copper gets oxidised to form copper ions
at cathode: copper ions gets reduced to form solid copper
the eletrolyte doesn’t change concentration because Cu electrode is oxidised to form Cu ion and Cu ion is reduced at cathode

Question 17

Hydrogen-fuel cells

Answer 17

uses hydrogen and oxygen to produce electricity with water as its only product

Question 18

advantages of hydrogen fuel cells in comparison to gasoline

Answer 18

No vehicle emissions other than water vapor. Fuel economy equivalent to about twice that of gasoline vehicles. Hydrogen is abundant, and can be made from renewable energy.

Question 19

Disadvantages of hydrogen fuel cells

Answer 19

Expensive.
Acceptable range requires extremely-high-pressure, on-board hydrogen storage.
Few places to refuel.
Lack of infrastructure to support the distribution of hydrogen.
Currently hydrogen fuel is made from nonrenewable natural gas in a process that creates enormous CO2 emissions.