Topic 4.1
What does it mean to use a fuel as a 'feedstock'?
It means using the fuel as a raw material in the chemical industry.
State two disadvantages of desalination.
Desalination is energy-intensive and generates brine waste that can harm marine ecosystems when discharged.
Define macronutrients in the context of soil chemistry.
Nutrients required in large quantities (e.g. N, P, K, Ca, Mg, S) for plant growth and metabolic function.
Given a molecule with a C=C bond, is it likely to undergo addition or condensation polymerisation?
It is likely to undergo addition polymerisation. The C=C bond in alkenes can break to allow the formation of single bonds between monomer units, creating long polymer chains without releasing any by-products.
If a product is removed from an equilibrated system, how will the system respond?
Le Chatelier's principle explains that a decrease in the concentration of a product will cause the system to shift equilibrium to favour the reaction that increases the product concentration, to replace the lost product. The position of equilibrium will shift to the right, favouring the forward reaction, to increase product concentration
What is one disadvantage of relying solely on solar and wind energy?
They are intermittent and weather-dependent.
What is flocculation in water treatment?
Flocculation is the process where destabilised particles aggregate into larger clumps (flocs), which settle out more easily during sedimentation.
How does nitrogen benefit plant growth?
Nitrogen is essential for amino acids, nucleic acids, and chlorophyll; it supports protein synthesis and vegetative growth.
Compare the extraction methods for sodium and iron.
Sodium, being highly reactive, is extracted by electrolysis of molten sodium chloride: 2NaCl(l) → 2Na(l) + Cl₂(g). Iron, being less reactive, is extracted by reduction of Fe₂O₃ with carbon in a blast furnace.
What influence does a catalyst have on the rate of a reaction?
A catalyst may either offer an alternative reaction pathway with a lower activation energy, saving energy costs; or by offering a surface or site for the reaction with controls the orientation of one molecule
What is one major challenge of storing hydrogen fuel?
It requires high pressure or low temperature for storage.
How do zeolites soften water?
Zeolites replace Ca²⁺₍ₐq₎ and Mg²⁺₍ₐq₎ ions with Na⁺₍ₐq₎ ions through ion exchange, preventing the formation of scale and improving soap efficiency.
What happens when Na⁺ levels in soil water are too high?
Na⁺ displaces nutrient cations from clays, leading to nutrient loss and soil structure degradation.
How do the chemical properties of thermoplastic and thermoset polymers differ when heated?
Thermoplastics soften upon heating due to weak intermolecular forces between polymer chains, allowing them to be reshaped multiple times. Thermosets, however, have covalent cross-links between chains, so they do not soften when heated and will instead degrade or char, making them permanently hard and inflexible.
What does a zero gradient represent?
A reaction that has either stopped or reached equilibrium
Why is incomplete combustion more likely with long-chain hydrocarbons?
Due to poor oxygen access and more bonds to break.
Explain how polymers and metal salts differ in flocculation.
Metal salts neutralise particle charges, while polymers form physical bridges between particles to build larger flocs.
What is the Haber–Bosch process?
A synthetic process that combines N₂ and H₂ to produce NH₃, which is used to make nitrogen fertilisers.
What is one disadvantage of using electrolysis in metal extraction?
Electrolysis is very energy-intensive, making it expensive. It often requires electricity generated from fossil fuels, contributing to greenhouse gas emissions and increasing environmental impact.
Write an equation showing the formation of sulphuric acid from sulphur trioxide and water:
SO3 + H2O = H2SO4
What specific heat capacity value is commonly used for water in calorimetry?
4.18 J/g°C
Write the equilibrium equation for chlorine reacting with water.
Cl₂₍g₎ + H₂O₍ₗ₎ ⇌ HOCl₍ₐq₎ + HCl₍ₐq₎
Why are clay soils more fertile than sandy soils?
Clays have higher surface area and charge, allowing greater nutrient and water retention.
Why are unreactive metals like gold found in their elemental form?
Unreactive metals, such as gold and platinum, are low in the activity series and have a low tendency to form positive ions. They do not readily oxidise or react with substances in the environment, so they are often found in their native, metallic state rather than as compounds.
What should answers using Le Chatelier's principle include?
1. Reference to Le Chatelier's principle
2. The change that has been made
3. A general statement as to what any system would do
4. A specific statement as to which way the position of equilibrium will shift