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Processes Flashcards

Extraction of Fe, extraction of Al, the Harbor process, the Contact process

1
Q
A
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2
Q

What is the primary ore used for extracting iron?

A

The primary ore used is hematite, which contains iron(III) oxide.

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3
Q

What primary reaction occurs in the extraction of Fe?

A

The primary reaction is the reduction of iron(III) oxide (Fe₂O₃) using carbon (coke) in a blast furnace.
The reaction can be summarized as follows: Fe2O3 (s) + 3CO (g) → 2Fe (I) + 3CO2 (g)

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4
Q

What is the role of carbon (coke) in the extraction of iron?

A

Carbon acts as a reducing agent, reacting with hematite in a blast furnace to produce iron and carbon dioxide.

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5
Q

What is the overall reaction for the extraction of iron from iron(III) oxide?

A

The overall reaction is: Iron(III) oxide + Carbon → Carbon dioxide + Iron.

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6
Q

Why is carbon monoxide a more effective reducing agent in the extraction process?

A

Carbon monoxide is more effective because it is a gas, allowing it to mix easily with solid hematite.

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7
Q

What impurities are commonly found in hematite, and how are they removed during iron extraction?

A

Impurities such as silicon dioxide are removed by adding calcium carbonate (limestone), which forms calcium silicate (slag) when it reacts with calcium oxide.

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8
Q

What environmental concern is associated with the extraction of iron?

A

The iron extraction process generates significant amounts of carbon dioxide, contributing to climate change.

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9
Q

What is done with the slag produced during the iron extraction process?

A

The slag can be repurposed for road surfacing due to its lower density and practical applications.

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10
Q

In the extraction of iron, what is the reducing agent?

A

Carbon: it is taking away the oxygen

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11
Q

In the extraction of iron, what is the oxidizing agent?

A

The hematite: it is providing the oxygen

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12
Q

In the extraction of iron, what is being oxidized?

A

The carbon

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13
Q

In the extraction of iron, what is being reduced?

A

The hematite

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14
Q

What is the first step in the extraction of iron from hematite?

A

Carbon (coke) and oxygen for carbon dioxide

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15
Q

Why is the reaction between carbon and oxygen essential in the extraction of iron?

A

This reaction is essential because it produces carbon dioxide and generates the heat needed for the subsequent reactions. (exothermic) The heat facilitates the reduction of iron(III) oxide by carbon monoxide, which is produced in the next steps.

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16
Q

What is the 2nd step in the extraction of iron?

A

The reduction of carbon dioxide to carbon monoxide:
CO2 (g) + C (s) → 2CO (g)

It is carbon monoxide that is the reducing agent.

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17
Q

What is the last step in the extraction of iron?

A

The reduction of iron(III) oxide by carbon monoxide:
Fe2O3 (s) + 3CO (g) → 2Fe (I) + 3CO2 (g)

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18
Q

What is the primary impurity found in iron ore during extraction?

A

The primary impurity is silicon dioxide (SiO₂), commonly found in the form of sand or rock within the iron ore.

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19
Q

Why do the impurities in hematite need to be removed in the extraction of iron?

A

Because, it would make the iron weaker

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20
Q

How is silicon dioxide removed during the extraction of iron?

A

Silicon dioxide is removed by adding limestone (calcium carbonate) to the blast furnace. It reacts with the impurity to form calcium silicate (slag).

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21
Q

What reaction occurs when limestone is added to the blast furnace to remove impurities?

A

The thermal decomposition of calcium carbonate (limestone) to produce calcium oxide:
CaCO3 (s) → CaO (s) + CO2 (g)

The formation of slag:
CaO (s) + SiO2 (s) → CaSiO3 (l)

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22
Q

What is coke?

A

Carbon

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23
Q

What is slag?

A

Calcium silicate (CaSiO3)

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24
Q

What is the symbol for silicone dioxide?

A

SiO2

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25
What happens to the slag produced from the removal of impurities?
The slag is less dense than molten iron, so it floats on top and can be easily removed. It can be repurposed for making road surfaces and other applications.
26
How is Al extracted?
Using electrolysis because it is more reactive than C. The Al compound is melted (requires lots of energy).
27
What is the general rule for reactivity of ions in electrolysis?
More reactive ions will preferentially discharge over less reactive ions during electrolysis.
28
What is the name of the ore from which aluminum is extracted?
The ore is called bauxite, which mainly contains aluminum oxide.
29
Why does aluminum oxide have a high melting point?
Aluminum oxide has a high melting point due to strong electrostatic forces between the aluminum ions (Al³⁺) and oxide ions (O²⁻).
30
What type of electrodes are used in the electrolysis of aluminum oxide?
Graphite electrodes are used in the electrolysis of aluminum oxide.
31
What products are formed at the cathode during the electrolysis of aluminum oxide?
Molten aluminum metal is produced at the cathode. => can then be frozen and molded
32
What happens at the anode during the electrolysis of aluminum oxide?
Oxygen gas is produced at the anode, which reacts with the graphite electrode to form carbon dioxide. The anodes erode over time due to the reaction with oxygen and therefore needs to be replaced over time.
33
What are the downsides of the extraction of Al using electrolysis?
* High energy demand => usually from non-renewable recourses (bad for environment) * Expensive (because of high energy)
34
Why do anodes need to be replaced during aluminum electrolysis?
The anodes erode over time due to the reaction with oxygen, producing carbon dioxide.
35
Describe the process occurring at the cathode during the extraction of Al.
Aluminum ions (Al³⁺) gain three electrons to become aluminum metal (Al), which is a reduction process.
36
Describe the process occurring at the anode during the extraction of Al.
Oxide ions (O²⁻) lose two electrons to form oxygen gas (O₂) during the oxidation process.
37
Why is aluminum extraction economically significant despite its high energy costs?
Aluminum is lightweight and strong, making it valuable for industries such as aerospace.
38
What factor contributes to the huge size of industrial electrolysis cells for aluminum extraction?
To produce large quantities of aluminum economically, industrial cells are significantly larger, often compared to the size of a swimming pool.
39
What is the basic reaction taking place during the electrolysis of aluminum oxide?
The breakdown of aluminum oxide (Al2O3) into aluminum and oxygen gas.
40
Draw a diagram of the extraction of Al
41
What is the symbol equation fro what occures at the anode and cathode during the extraction fo Al?
42
How can high energy demands be lowered in th extraction fo Al?
By adding cryolite (Na3AlF6)
43
What is cryolite?
Cryolite is a mineral composed of sodium aluminum fluoride (Na3AlF6) used as an electrolyte in the extraction of aluminum.
44
Why is cryolite added to aluminum oxide during electrolysis?
Cryolite lowers the melting point of aluminum oxide, making the process more energy-efficient.
45
How does the addition of cryolite reduce energy demands?
* Cryolite helps lower the melting point of aluminum oxide from around 2072°C to about 1000-1200°C, making the process more energy-efficient. (less energy needed to keep moletn) * By increasing the conductivity of the molten aluminum oxide, cryolite facilitates a more efficient transfer of electricity.
46
What are the chemical components of cryolite?
Cryolite is primarily composed of sodium aluminum fluoride (Na3AlF6).
47
What additional benefit does cryolite provide in the context of aluminum extraction?
It reduces environmental impact by lowering energy requirements, which can minimize reliance on non-renewable energy sources.
48
In what physical state is cryolite used during the aluminum extraction process?
Cryolite is used in its molten state as part of the electrolyte mixture.
49
Why does cryolite help to lower the mpt of Al2O3?
Because the cryolite contains ions with much lower charg. Mixing these ions in the electrolyte lowers the mpt due to weaker electrostatic forces.
50
Why does cryolite increase the conductivity of Al2O3 in the extraction fo Al?
* It decreases the resistance of electricity * Waste less electrical energy
51
Is cryolite a catalyst?
NOOOO!!! * It is not interfering with the reaction * Does not affect the activation energy * Does not speed up rate of reaction
52
What is the Haber process primarily used for?
The Haber process is used to synthesize ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂).
53
What are the raw materials used in the Haber process?
The raw materials are nitrogen, which is abundantly found in the air, and hydrogen, which can be obtained from natural gas.
54
What is the chemical equation for the Haber process?
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
55
What is the optimum temperature for the harbor process?
The reaction is exothermic. A **low temperature** favors the forward reaction (formation of ammonia).
56
What is the optimum pressure for the harbor process?
A **high pressure** is optimal because there are fewer mols of gaseous products (than reactants).
57
What catalyst is used in the harbor process?
Powdered Iron. It is used to reduce the time taken to reach equilibrium. It is powdered to increase its surface area and therefore increase rate even further.
58
What is the actual temperature used in the harbor process?
A compromise of 450°C is used. This is a medium temperature. Reason: A low temp. gives a high yield, but the rate would be too slow. A high temperature would react at a high rate but would yield a low amount. The temp. used is "in the middle".
59
What is the actual pressure used in the harbor process?
a fairly high pressure of 200Atm. A high pressure increases the yield and overall rate, but a very high pressure requires high running costs. The small increase in yield is cancelled out by the higher running cots.
60
Using actual conditions how high is the yield for the harbor process?
The yield is only about 20%.
61
What happens to the unreacted nitrogen and hydrogen used in the harbor process?
They are recycled to prevent expensive extraction from raw materials.
62
What is the primary purpose of the Contact
To manufacture sulfuric acid.
63
What are the three main steps in the Contact Process?
1. sulfur + oxygen → sulfur dioxide S + O2 → SO2 2. sulfur dioxide + oxygen ⇌ sulfur trioxide 2SO2 + O2 ⇌2SO3 3. SO3 + H2O → H2SO4 sulfur trioxide + water → sulfuric acid (reaction is heavily exo. therefore acid could boil = dangerous) **SOLUTION** SO3 + H2SO4 → H2S2O7 (oleum) sulfur trioxide + sulfuric acid → disulfuric acid H2O + H2S2O7 → 2H2SO4 water + disulfuric acid → sulfuric acid This is less exothermic
64
What is the main step of the contact process?
sulfur dioxide + oxygen ⇌ sulfur trioxide 2SO2 + O2 ⇌2SO3
65
What is the optimum pressure of the contact process?
A **high pressure** because there are fewer mols of gaseous products than reactants.
66
What is the optimum temperature of the contact process?
A **low temp.** because the forward reaction is exothermic; therefore, low temp. is favorable.
67
Is the contact process exothermic or endothermic?
Exothermic
68
What is the catalyst for the contact process?
Powdered vanadium (V) oxide because adding a catalyst decreases the time taken to reach equilibrium. It is powdered to increase its SA and therefore increases the rate even further.
69
What is the actual pressure of the contact process?
**1-2Atm (low)**. A high pressure increases the yield and the overall rate, but the contact process has a 99% yield even at low pressure. A higher pressure is not worth the additional cost. **200 kPa**
70
What is the actual temp. of the contact process?
**400°C (medium)** . A low temp. gives a high yield, but the rate would be too slow. A high temp. would produce a low yield. The temp. used is "in the middle".
71
What is the yield of the contact process?
The yield is very high even at less the optimum conditions.
72
73
What are 2 methods of the manufacture of ethanol?
a. direct hydration of ethene b. fermentation of sugars
74
Advantages of direct hydration of ethene
* continuous process * product is pure (no seperation needed)
75
Disadvantages of direct hydration of ethene
* high energy demand (fossil fuel power stations) * ethene comes from cracking (and alkanes need to be extracted from crude oils) * alkanes are non-rewnewable
76
Describe the direct hydration of ethene
* ethene (double bond) and water make ethanol. * This process requires a concentrated catalyst => H₂SO₄ => H₃PO₄ * This process requires heat (600°C) * This reaction makes 100% ethanol
77
What is 100% ethanol used for?
It is used as a disinfectant/solvent
78
Advantages of fermentation of sugars
* sugar and fruit provide flavor * renewable recources * low energy demand
79
Disadvantages of fermentation of sugars
* batch process (**slow**) * product is a mixture => ethanol produced needs to be separated if a higher conc. is desired
80
Describe the fermentation of sugars
* sugar makes ethanol and carbondioxide * Reaction requires yeast * uses sugar (from fruit) * the max. concentration of the result is 15% because: => fruit is not 100% sugar => ethanol will kill yeast, stopping the process => distillation can produce more concentrated ethanol
81
What is the general formula for the directy hydration of ethene?
ethene + water ==600°C==H₂SO₄/H₃PO₄==> ethanol
82
What are the 2 catalysts which can be used for the direct hydration of ethene?
H₂SO₄ OR H₃PO₄
83
What is the general fromula of the fermentation of sugars
sugar =yeast=> ethanol + carbon dioxide
84
What is the general symbol formula of the fermentation of sugars?
C₆H₁₂O₆ =yeast=> C₂H₅OH + 2CO₂
85
How do you make an ester?
alcohol + carboxylic acid
86
How do you make a condensation polyester?
dialcohol + ethandioic acid
87

Chemistry IGCSE (16 decks)

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