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AQA GCSE CHEMISTRY > c15 Using our resources > Flashcards

c15 Using our resources Flashcards

1
Q

What can ammonia be used to make?

A

fertilisers
, explosives and dyes.

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2
Q

What is the Haber process?

A

The industrial chemical process that makes ammonia by reacting nitrogen and hydrogen together.

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3
Q

The haber process is a ________ reaction

A

reversible

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4
Q

What is the formula for the haber process?

A

N2(g) + 3H2(g) ⇌ 2NH3(g)

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5
Q

How are the raw materials for the production of ammonia collected?

A

Nitrogen-Naturally present in the atmosphere
Hydrogen-Collected from Natural Gas

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6
Q

What are the steps of the Haber Process?

A

nitrogen (extracted from the air) and hydrogen (obtained from natural gas) are pumped through pipes the pressure of the mixture of gases is increased to 200 atmospheres
the pressurised gases are heated to 450°C and passed through a tank containing an iron
catalyst the reaction mixture is cooled so that ammonia liquefies and can be removed unreacted nitrogen and hydrogen are recycled

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7
Q

What is the atom economy for the Haber process and why is it like this?

A

100% atom economy so no waste by-products formed in reaction, no pollution from by-products, no energy required for their disposal

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8
Q

What happens to unreacted nitrogen and hydrogen in the Haber Process?

A

It gets recycled back into the reaction vessel to react to form Ammonia again

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9
Q

Why is 200 atmospheres used in HP?

A

When the pressure is higher the equilibrium shifts to the side with the least amount of gases- in this case to the side with ammonia- increasing the yield. However higher pressures are expensive and costly so 200 atms is chosen as a compromise

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10
Q

Why is an Iron catalyst used in HP?

A

An Iron catalyst speeds up the rate of the forward and reverse reactions equally. This reduces the time taken for the system to reach equilibrium but it does not affect the position of equilibrium or the yield of ammonia.

Using a catalyst in the Haber process means that a lower temperature can be used whilst keeping the rate of reaction high. A lower temperature helps to keep the yield high.

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11
Q

Why is a temperature of 450C chosen for HP?

A

When the temperature is increased, the position of equilibrium moves in the endothermic direction to reduce the temperature.

In the Haber process, the forwards reaction is
exothermic, so the reverse reaction is endothermic.

This means that as the temperature is increased, the position of equilibrium moves to the left, and the yield of ammonia decreases.

It may seem sensible to use a very low temperature in order to maximise the yield of ammonia but lower temperatures reduce the rate of reaction. The temperature chosen is a compromise between yield and rate.

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12
Q

What causes corrosion of metals?

A

Corrosion is caused by chemical reactions between the metal and substances in the environment.

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13
Q

Why is rusting a problem for iron?

A

Rust is soft and flakes off, exposing fresh iron to further corrosion, unlike aluminium’s protective oxide layer.

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14
Q

What two substances are needed for iron to rust?

A

Both air (oxygen) and water are required for iron to rust.

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15
Q

How can rust be prevented by coating iron?

A

Coatings like paint, oil, grease, or plastic create a barrier to keep air and water away from iron.

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16
Q

Why does a scratched coating of zinc still protect iron?

A

Zinc is more reactive than iron, so it oxidises first, sacrificially protecting the iron (galvanisation).

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17
Q

What is sacrificial protection?

A

Sacrificial protection uses a more reactive metal (e.g., zinc) to oxidise instead of the iron, even if the coating is damaged.

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18
Q

Where is sacrificial protection commonly used?

A

It is used in harsh conditions like seawater or underground pipes.

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19
Q

Why do sacrificial metal bars need replacing?

A

The bars (e.g., magnesium) corrode over time and must be replaced to continue protecting the iron.

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20
Q

What is galvanisation?

A

Galvanisation is the process of coating iron with zinc to prevent rusting through sacrificial protection.

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21
Q

What is bronze?

A

Bronze is an alloy of copper and tin, first made around 5500 years ago. Bronze is tough and resistant to corrosion.

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22
Q

What is brass?

A

Brass is an alloy of copper and zinc, known for being hard yet workable.

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23
Q

Why is aluminium alloyed with other elements?

A

Alloying improves aluminium’s properties, creating lightweight but strong materials for uses like aircraft.

24
Q

Why is gold alloyed with copper for jewellery?

A

Pure gold is soft; alloying with copper increases hardness and allows for different shades.

25
How is gold purity measured, and what does 18-carat gold mean?
Gold purity is measured in carats (24-carat = 99.9% pure); 18-carat gold is 75% gold.
26
Compare high-carbon and low-carbon steels.
High-carbon steel is strong but brittle; low-carbon steel is softer, more malleable, and less likely to shatter
27
What are alloy steels, and why are they more expensive?
Alloy steels contain 1–5% other metals (e.g., nickel, tungsten), enhancing specific properties but increasing cost
28
Why is nickel-steel used in bridges and armour plating?
Nickel-steel resists stretching forces, making it ideal for bridges, bicycle chains, and armour.
29
What makes tungsten steel suitable for drill bits?
Tungsten steel withstands high temperatures, perfect for high-speed tools like drill bits.
30
What are stainless steels, and what properties do they have?
Stainless steels (chromium-nickel alloys) resist corrosion, are hard/strong, and do not rust. They are used in cutlery, cooking utensils, chemical reaction vessels, and pipework. It withstands high temperatures, pressures, and corrosive chemicals, despite being costly.
31
What is a polymer?
A polymer is a large molecule made by joining many small monomer units together.
32
What is the difference between high-density (HD) and low-density (LD) poly(ethene)?
HD poly(ethene) has straighter chains that pack closely, making it stronger and denser, while LD poly(ethene) has branched chains and lower density.
33
What is the difference between the way that high-density (HD) and low-density (LD) poly(ethene) are produced?
LD poly(ethene) is made using very high pressures and a trace of oxygen, resulting in branched polymer chains. HD poly(ethene) is made using a catalyst at 50°C and slightly raised pressure, producing straighter, closely packed chains.
34
What are thermosoftening polymers?
Thermosoftening polymers melt when heated and harden when cooled due to weak intermolecular forces between chains. The weak forces between chains break when heated, allowing the polymer to be reshaped.
35
What are thermosetting polymers?
Thermosetting polymers have strong covalent cross-links between chains, preventing them from melting when heated. The covalent cross-links between chains remain intact, making the polymer rigid and heat-resistant.
36
What are the main raw materials for making soda-lime glass?
Sand (SiO₂), limestone (CaCO₃), and sodium carbonate (Na₂CO₃).
37
Why is recycled glass used in glass production?
It reduces waste and can make up to 30% of the raw material mixture.
38
Describe the atomic structure of glass.
Glass has a disordered (amorphous) structure where particles are "frozen" randomly, unlike crystals. Its amorphous structure lacks flexibility, making it brittle under stress.
39
What is borosilicate glass, and why is it used for ovenware?
Made from sand and boron trioxide (B₂O₃); it melts at higher temperatures than soda-lime glass, making it heat-resistant.
40
How are clay ceramics made?
Wet clay is molded into shape and fired at ~1000°C, driving out water and forming strong bonds.
41
Why are ceramics brittle?
Distorting their layered structure can align like-charged ions, causing repulsion and cracks.
42
What bonds are present in ceramics?
Ionic bonds between metal/non-metal ions and some covalent bonds between non-metal atoms .Their strong ionic/covalent bonds make them inert and poor conductors.
43
What is a composite material?
A combination of two materials (e.g., matrix + reinforcement) to improve properties for specific uses.
44
How does glass-ceramic composite overcome brittleness?
Molten glass fills gaps between ceramic crystals, preventing crack propagation.
45
What is fibreglass, and why is it used in kayaks?
Glass fibers embedded in polymer resin; it’s tough, flexible, waterproof, and lightweight.
46
What are two examples of wood composites?
Plywood: Layers of wood with alternating grain directions to resist splitting. MDF(Medium density fibreboard): Compressed woodchips bound with resin, splinter-resistant for intricate shapes.
47
How is reinforced concrete made stronger?
Steel rods are embedded in concrete to resist bending forces (tension).
48
Why is concrete strong in compression but weak in tension?
Hardness comes from cement binding, but it cracks under stretching forces without reinforcement.
49
What is concrete made from
cement, sand ,gravel mixed by water
50
How to make fertilisers in the lab?
Collect 25 cm³ of ammonia solution in a small conical flask. Use a pipette and filler to measure this accurately. Add dilute sulfuric acid, 1 cm³ at a time, from a burette. After adding each cm³ of acid, swirl your flask Dip a glass rod into the solution. Then test a drop of the solution on a small piece of blue litmus paper on a spotting tile. Keep adding acid until the litmus just turns pink. Repeat the titration until you get two volumes of sulfuric acid within 0.1 cm³ of each other. These are called concordant results. Then pour the solution into an evaporating dish. Heat it on a water bath until about half of the water from the solution has evaporated off. (Do not let it boil dry.) Leave the rest of the solution to evaporate off slowly to leave crystals of ammonium sulfate. Alternatively,before all the water has evaporated off, you can filter off any crystals and dab them dry with another piece of filter paper. Then leave them to dry under a clean piece of filter paper.
51
What are NPK fertilizers?
Fertilizers containing nitrogen (N), phosphorus (P), and potassium (K) to promote plant growth. No single compound contains all three, so formulations mix different compounds.
52
Why can't phosphate rock be used directly as fertilizer?
It's insoluble in water. Must be treated with acids (nitric, sulfuric, or phosphoric) to create soluble phosphate salts like ammonium phosphate or superphosphates.
53
How is phosphorus extracted for fertilizers?
Phosphate rock is treated with: Nitric acid → phosphoric acid + calcium nitrate → ammonium phosphate (with ammonia). Sulfuric acid → single superphosphate (Ca phosphate + Ca sulfate). Phosphoric acid → triple superphosphate (Ca phosphate).
54
How are potassium fertilizers obtained?
Mined as soluble salts (KCl, K₂SO₄), separated from impurities, and used directly.
55
Compare lab vs. industrial ammonium sulfate production:
Scale: Lab = small batches (grams); Industry = tonnes. Safety: Lab = dilute solutions; Industry = concentrated, high-pressure/temperature (explosion risk). Equipment: Lab = glass; Industry = stainless steel (corrosion-resistant). Process: Lab = titration + slow evaporation; Industry = continuous reaction towers + granulation. Product: Lab = needle-like crystals; Industry = uniform granules (prevents clumping)
56
Why is industrial production continuous?
Enables large-scale output with automated piping of reactants (e.g., spraying H₂SO₄ into NH₃ gas at 60°C).

AQA GCSE CHEMISTRY (16 decks)

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