Topic 7 Flashcards

Crude Oil & Fractional Distillation

Crude Oil & Fractional Distillation: read all 6 questions and answers

1. What is crude oil?
   A finite resource formed over millions of years from the remains of ancient marine organisms. It is a MIXTURE of many different hydrocarbons.
2. What is a hydrocarbon?
   A molecule made of hydrogen and carbon atoms ONLY. No other elements are present.
3. How is crude oil separated into useful fractions?
   By FRACTIONAL DISTILLATION. The oil is heated into a mixture of liquid and vapour, and the vapour enters a fractionating column (hot at the bottom, cool at the top). Hydrocarbons condense at different heights based on their boiling points.
4. As chain length increases, what happens to boiling point, viscosity, and flammability?
   Boiling point INCREASES (more intermolecular forces). Viscosity INCREASES (thicker). Flammability DECREASES (harder to ignite).
5. Why do longer hydrocarbons have higher boiling points?
   Longer chains have MORE INTERMOLECULAR FORCES between molecules, so more energy is needed to separate them.
6. Name the fractions from top to bottom of the column.
   Gases (LPG) → Petrol → Naphtha → Kerosene → Diesel → Fuel oil → Bitumen. Shortest chains and lowest boiling points at the TOP.

Alkanes

Alkanes: read all 4 questions and answers

1. What is the general formula for alkanes?
   CₙH₂ₙ₊₂. They are a homologous series of SATURATED hydrocarbons - only single C-C bonds.
2. Name the first four alkanes and their formulae.
   Methane (CH₄), Ethane (C₂H₆), Propane (C₃H₈), Butane (C₄H₁₀).
3. What does 'saturated' mean?
   Contains only SINGLE covalent bonds (C-C and C-H). No double bonds. This means alkanes cannot react by addition.
4. What is a homologous series?
   A family of compounds with the SAME general formula, SIMILAR chemical properties, and a gradual TREND in physical properties. Each member differs by CH₂.

Combustion & Pollutants

Combustion & Pollutants: read all 5 questions and answers

1. What are the products of complete combustion of a hydrocarbon?
   Carbon dioxide (CO₂) and water (H₂O). Plenty of oxygen is needed. E.g. CH₄ + 2O₂ → CO₂ + 2H₂O.
2. What happens during incomplete combustion?
   Limited oxygen supply produces carbon monoxide (CO) and/or carbon (soot/particulates) instead of CO₂. E.g. 2CH₄ + 3O₂ → 2CO + 4H₂O.
3. Why is carbon monoxide dangerous?
   CO is TOXIC - it binds to haemoglobin in red blood cells, preventing them from carrying oxygen. It is also colourless and odourless, making it hard to detect.
4. Name four pollutants from burning fossil fuels.
   1. CO₂ - greenhouse gas → climate change. 2. CO - toxic gas. 3. SO₂ - from sulfur impurities → acid rain. 4. NOₓ - from N₂ + O₂ at high temps → acid rain, smog. 5. Particulates (soot) - respiratory problems, global dimming.
5. How are nitrogen oxides (NOₓ) formed?
   At HIGH TEMPERATURES in engines, nitrogen and oxygen from the air react: N₂ + O₂ → 2NO. This is NOT from the fuel itself.

Cracking & Alkenes

Cracking & Alkenes: read all 6 questions and answers

1. What is cracking?
   Breaking down LONG-CHAIN hydrocarbons into SHORTER, more useful ones. It produces shorter alkanes (fuels) and alkenes (for making polymers).
2. What are the two methods of cracking?
   1. CATALYTIC cracking: vapour passed over a hot zeolite catalyst at 600-700°C. 2. STEAM cracking: vapour mixed with steam and heated to over 800°C (no catalyst needed).
3. What is the general formula for alkenes?
   CₙH₂ₙ. They are UNSATURATED hydrocarbons - they contain a C=C double bond.
4. How do you test for an alkene?
   Add BROMINE WATER. If it is an alkene, the bromine water turns from ORANGE to COLOURLESS (decolourises). An addition reaction occurs across the C=C double bond.
5. Name the first three alkenes.
   Ethene (C₂H₄), Propene (C₃H₆), Butene (C₄H₈).
6. Do alkanes decolourise bromine water?
   NO. Alkanes are saturated (no C=C double bond), so they cannot undergo addition reactions with bromine water. The solution stays orange.

Alcohols & Carboxylic Acids (Chemistry Only)

Alcohols & Carboxylic Acids: read all 7 questions and answers

1. What is the functional group of alcohols?
   -OH (hydroxyl group). General formula: CₙH₂ₙ₊₁OH.
2. Name the first three alcohols.
   Methanol (CH₃OH), Ethanol (C₂H₅OH), Propanol (C₃H₇OH).
3. Give four reactions of alcohols.
   1. Combustion (burn → CO₂ + H₂O). 2. React with sodium → hydrogen gas. 3. Dissolve in water → neutral solutions. 4. Oxidation → can form carboxylic acids.
4. Compare fermentation and hydration for making ethanol.
   Fermentation: glucose + yeast, ~37°C, slow, impure, renewable (carbon neutral). Hydration: ethene + steam, 300°C/60 atm/H₃PO₄ catalyst, fast, pure, non-renewable (crude oil).
5. What is the functional group of carboxylic acids?
   -COOH (carboxyl group). General formula: CₙH₂ₙ₊₁COOH. They are WEAK acids - they partially ionise in water.
6. Name the first three carboxylic acids.
   Methanoic acid (HCOOH), Ethanoic acid (CH₃COOH - vinegar), Propanoic acid (C₂H₅COOH).
7. What is an ester? How is it formed?
   An ester = alcohol + carboxylic acid → ester + water. This is called ESTERIFICATION. Esters have fruity smells and are used in flavourings and perfumes. Name: alcohol-yl acid-anoate.

Addition Polymers

Addition Polymers: read all 5 questions and answers

1. What is addition polymerisation?
   Many small alkene MONOMERS join together by opening their C=C double bonds to form a long-chain POLYMER. No other product is formed - only the polymer.
2. Give three examples of addition polymers.
   Poly(ethene) - from ethene. Poly(propene) - from propene. Poly(chloroethene) / PVC - from chloroethene.
3. How do you draw the repeat unit from the monomer?
   Open the C=C double bond to form two single bonds (one on each side). The atoms attached to the carbons stay the same. Add extending bonds on each end.
4. How do you identify the monomer from a polymer repeat unit?
   Replace the extending single bonds with a C=C double bond. The two carbons in the backbone become the double-bonded carbons of the monomer.
5. Why are addition polymers an environmental problem?
   Most are NON-BIODEGRADABLE - they persist in landfill and the environment for hundreds of years. They are difficult to dispose of sustainably.

Condensation Polymers (Chemistry Only)

Condensation Polymers: read all 4 questions and answers

1. What is condensation polymerisation?
   Monomers with two reactive functional groups join together with the elimination of a small molecule (usually water or HCl) as a by-product. Monomers can be two different types or a single type with two different functional groups (e.g. amino acids).
2. What monomer combinations make polyesters and polyamides?
   Polyester: dicarboxylic acid + diol. Polyamide (nylon): dicarboxylic acid + diamine.
3. Name three natural condensation polymers.
   1. Proteins - from amino acid monomers. 2. DNA - from nucleotide monomers. 3. Starch/cellulose - from sugar monomers.
4. What is the key difference between addition and condensation polymerisation?
   Addition: only the polymer is formed (no by-product); uses monomers with C=C double bonds. Condensation: polymer plus a small molecule (such as H₂O or HCl) is formed; monomers contain two reactive functional groups.