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Question 1

What do metal oxides and hydroxides generally behave as?

Answer 1

Bases and neutralise acids

This property is important in various chemical reactions and agricultural practices.

Question 2

What is the definition of a base?

Answer 2

A substance that accepts hydrogen ions (H+)

Bases are also referred to as proton acceptors.

Question 3

What can the oxide ion in metal oxides do?

Answer 3

Accept protons and neutralise acids

An example is calcium oxide reacting with sulfuric acid.

Question 4

What is the reaction between calcium oxide and sulfuric acid?

Answer 4

CaO(s) + H2SO4(aq) → CaSO4(s) + H2O(l)

This reaction demonstrates the neutralising effect of calcium oxide.

Question 5

What is calcium oxide commonly called?

Answer 5

Lime

Lime is used in agriculture to neutralise acidic soil.

Question 6

What happens if the pH of soil is too low?

Answer 6

Plants will tend to absorb toxic ions that affect root growth

Maintaining proper soil pH is crucial for healthy plant growth.

Question 7

What are amphoteric oxides?

Answer 7

Oxides that can behave as either acids or bases

Common examples include aluminium oxide.

Question 8

Will aluminium oxide dissolve in water?

Answer 8

No

It reacts with acids and bases instead.

Question 9

What is the reaction of aluminium oxide with hydrochloric acid?

Answer 9

Al2O3(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2O(l)

This reaction shows aluminium oxide acting as a base.

Question 10

What does aluminium oxide react with to form aluminates?

Answer 10

Bases, such as NaOH

This reaction is part of the Bayer process.

Question 11

What is the formula for the reaction of aluminium oxide with sodium hydroxide?

Answer 11

Al2O3 + 2NaOH + 3H2O → 2NaAl(OH)4

This is used to convert bauxite into aluminium oxide.

Question 12

What do metal oxides form when they react with water?

Answer 12

Hydroxides

For example, magnesium oxide forms magnesium hydroxide.

Question 13

What is the reaction for magnesium oxide with water?

Answer 13

MgO(s) + H2O(l) → Mg(OH)2(s)

This reaction illustrates the formation of a hydroxide.

Question 14

What is magnesium hydroxide commonly used for?

Answer 14

As an antacid to relieve indigestion and heartburn

It neutralises hydrochloric acid in the stomach.

Question 15

What is the reaction of magnesium hydroxide with hydrochloric acid?

Answer 15

Mg(OH)2(s) + 2HCl(aq) → MgCl2(aq) + 2H2O(l)

This shows magnesium hydroxide acting as a base.

Question 16

What is calcium hydroxide used for in the chemical industry?

Answer 16

To neutralise acidic effluent

An example is its use with dilute sulfuric acid.

Question 17

What is the reaction for calcium hydroxide with sulfuric acid?

Answer 17

Ca(OH)2(s) + H2SO4(aq) → CaSO4(s) + 2H2O(l)

This reaction demonstrates calcium hydroxide’s neutralising ability.

Question 18

What is alumina?

Answer 18

A form of aluminium oxide found in the mineral bauxite

It is extracted and purified using the Bayer process.

Question 19

What are the stages in the Bayer process?

Answer 19

1. Crush the bauxite.
2. React with NaOH(aq) at 170°C.
3. Filter out solid impurities.
4. Allow to crystallise to form Al(OH)3.
5. Heat in rotary kiln to form Al2O3.

This process is essential for producing aluminium.

Question 20

What is the Hall-Héroult process used for?

Answer 20

To form aluminium by electrolysis

This process utilizes alumina extracted from the Bayer process.

Question 21

What are refractory materials?

Answer 21

Materials that retain strength and chemical stability at high temperatures

Alumina is used as a refractory material in kilns.

Question 22

What are the two low-density and corrosion-resistant metals discussed?

Answer 22

Aluminium and titanium

Both metals form strong alloys.

Question 23

What is the primary ore of aluminium?

Answer 23

Bauxite

Question 24

What process is used for the extraction of aluminium?

Answer 24

Hall-Héroult process

Question 25

What is the main ore of titanium?

Answer 25

Rutile

Question 26

What is titanium(IV) dioxide's chemical formula?

Answer 26

TiO2

Question 27

True or False: Titanium is extracted by electrolysis like aluminium.

Answer 27

False

Question 28

What is the Kroll process used for?

Answer 28

Extraction of titanium

Question 29

What are the key components heated together in the Kroll process?

Answer 29

Titanium(IV) dioxide, coke, and chlorine

Question 30

At what temperature is the Kroll process conducted?

Answer 30

About 900°C

Question 31

What is formed during the Kroll process?

Answer 31

Titanium(IV) chloride

Question 32

Fill in the blank: Magnesium is used as a _______ agent in the Kroll process.

Answer 32

reducing

Question 33

What reaction occurs to produce titanium from titanium(IV) chloride?

Answer 33

TiCl4(g) + 2Mg(l) → Ti(s) + 2MgCl2(l)

Question 34

What is added to alumina in the Kroll process to lower the melting point?

Answer 34

Cryolite

Question 35

What is the purpose of the carbon lining in the steel tank of the Kroll process?

Answer 35

Acts as the negative electrode

Question 36

What is the outcome of the reduction of aluminium ions in the Kroll process?

Answer 36

Molten aluminium is formed

Question 37

What happens to oxide ions at the positive electrodes during the process?

Answer 37

They are oxidised to form oxygen gas

Question 38

What is a disadvantage of the Kroll process?

Answer 38

It is expensive and time-consuming

Question 39

How often do the carbon electrodes need to be replaced in the Kroll process?

Answer 39

Regularly

Question 40

List some properties of titanium.

Answer 40

* High stiffness * High strength * Density of 4.51 g/cm³ * Corrosion resistant

Question 41

List some properties of aluminium.

Answer 41

* High stiffness * High strength * Density of 2.70 g/cm³ * Cheaper than titanium

Question 42

True or False: Titanium is less dense than aluminium.

Answer 42

False

Question 43

Why might aluminium be chosen over titanium for bicycle frames?

Answer 43

Lower cost and sufficient strength for the application

Question 44

Fill in the blank: Carbon fibre is a strong, rigid, low density, non-metal material used in _______.

Answer 44

bike frames

Question 45

Suggest a reason, other than cost, that explains why fewer frames are made from carbon fibre than aluminium.

Answer 45

Carbon fibre may not provide the same level of durability or ease of manufacturing.

Question 46

What is produced from the electrolysis of brine?

Answer 46

Chlorine, hydrogen, and sodium hydroxide ## Footnote These products are essential for various chemical processes.

Question 47

What reaction occurs at the positive electrode (anode) during the electrolysis of brine?

Answer 47

2Cl⁻(aq) → Cl₂(g) + 2e⁻ ## Footnote This reaction involves the oxidation of chloride ions.

Question 48

What reaction occurs at the negative electrode (cathode) during the electrolysis of brine?

Answer 48

2H⁺(aq) + 2e⁻ → H₂(g) ## Footnote This reaction involves the reduction of hydrogen ions.

Question 49

What remains in solution after the electrolysis of brine?

Answer 49

Sodium ions and hydroxide ions ## Footnote These ions form sodium hydroxide solution.

Question 50

What is the purpose of the diaphragm in a diaphragm cell?

Answer 50

It allows brine to pass but prevents chlorine and hydrogen gas from passing through ## Footnote This separation keeps gaseous products distinct.

Question 51

What is a major advantage of the membrane cell compared to the diaphragm cell?

Answer 51

Higher purity of sodium hydroxide produced ## Footnote The membrane cell uses an ion-exchange membrane that prevents contamination.

Question 52

Fill in the blank: The diaphragm cell is ______ to construct but requires regular replacement of the diaphragm.

Answer 52

cheaper

Question 53

True or False: The membrane cell has lower maintenance requirements than the diaphragm cell.

Answer 53

True

Question 54

What type of membrane does the membrane cell use?

Answer 54

Ion-exchange membrane ## Footnote This membrane allows positive sodium ions to pass but blocks negative chloride ions.

Question 55

What is a disadvantage of the diaphragm cell regarding energy usage?

Answer 55

Uses slightly more energy per tonne of chlorine produced ## Footnote This can affect the overall efficiency of the production process.

Question 56

What is the role of sodium chloride in the electrolysis process?

Answer 56

It is the electrolyte used in the process ## Footnote NaCl(aq) is crucial for the electrolysis of brine.

Question 57

What can be done to remove excess sodium chloride from sodium hydroxide solution?

Answer 57

Recrystallisation ## Footnote Sodium chloride is less soluble than sodium hydroxide, allowing for separation.