Electrochemistry

Question 1

What is a metallic conductor

Answer 1

Substances which carry electrical current due to delocalised electrons

Question 2

What are electrolytes of

Answer 2

Conduct electricity due to free moving ions when a lattic breaks down . Covalently bonded acids also form electrolyte solutions in water .

Question 3

What happens when current passes through an electrolyte

Answer 3

Ions move through substance so pick up electrons or give electrons to power supply resulting in a chemichal reaction that breaks down the electrolyte into elements . They are decomposed by the passage of an electric current ( electrolysis )

Question 4

Electrode

Answer 4

Metallic conductor that the power supply makes contact with the electrolyte

Question 5

Anode

Answer 5

Positive electrode attracts negative ions

Question 6

Cathode

Answer 6

Negative electrode , attracts positive ions metal will form here

Question 7

Where will hydrogen be discharged when an ionic compound is electrolysed in an aqueous solution

Answer 7

At cathode unless copper , silver or gold ions are present in solution as these will be discharged instead as the metal

Question 8

Where will oxygen be discharged

Answer 8

At the anode unless halide ions are present in high concentrations because they will be discharged as the halogen instead

Question 9

What are electrodes made from

Answer 9

Unreactive substances like graphite or platinum

Question 10

Reduction ocuurs at

Answer 10

Cathode , gain of electrons

Question 11

Oxidation occurs

Answer 11

At anode loss of electrons

Question 12

How is dilute sulphuric acid electrolysed

Answer 12

Hoffman voltameter as both products are gases and this allows the gas to be collected and measured . Produces hydrogen and oxygen .

Question 13

What happens when aqueous sodium chloride is electrolysed

Answer 13

H gas formed at cathode from ions in the water

Chlorine formed at anode as chlorine gas

Question 14

What happens when copper sulphate is electrolysed with graphite electrodes

Answer 14

Copper ions attracted to the cathode forming a salmon pink

Coating . Oxygen is produced at the anode

Question 15

What happens when copper sulphate is electrolysed with copper electrodes

Answer 15

Anode is impure copper and shrinks as copper atoms loose 2 electrons and the copper metal dissolves into Ye solution
Copper gains electrons at the cathode becoming pure copper atoms and the cathod grows in side coated with copper metal . Copper metal is transferred from anode to cathode , leaving impurities behind . These may fall to the bottom or dissolve in the electrolyte , remaining in solution

Question 16

What happens if the thing being electrolysed is Milton

Answer 16

Only one possible outcome will split into the two ions e.g. Molten zinc chloride forms zinc on cathode and chlorine on anode

Question 17

How do you calculate moles of electrons

Answer 17

Charge / 96500

Question 18

What are the uses of electrolysis

Answer 18

Extraction of reactive metals that are more reactive than carbon as ones lower in the reactivity series can be displaced using coke .
Purification of metals - removes traces of other elements in the metal
Electroplating - thin coating of another metal of the surface e.g. Silver playing or chromium plating steel as it doesn’t corrode . Object to be plated is the cathode and the solution contains the ions of the metal that the object is to be plated with .

Question 19

What is the Chlor alkali industry

Answer 19

Electrolysis of brine ( concentrated sodium hydroxide ) produces hydrogen chlorine and sodium hydroxide . This is carried out in a membrane cell with two electrodes in separate compartments partitioned by a permeable diaphragm which lets solutions slowly seep through . At the anode chlorine gas is fined , at the cathode hydrugen gas is formed . OH accumulates in cathode compartment with Na making sodium hydroxide solution . Diaphragm prevents hydroxide ions moving into the anode where they would react with the chlorine produced there

Question 20

What’s sodium hydroxide used for

Answer 20

Purify bauxite , make soap, manufacture ceramics and break down wood in paper reactions

Question 21

What’s chlorine used for

Answer 21

Bleach hydrochloride acid antiseptics PVC and sterilise water

Question 22

What hydrogen used for

Answer 22

The manufactur of amonium and margarine