chemistry paper 2

• Why might the rate of a reaction be considered the mean rate?

  The calculated rate is the average rate over the time measured.
• What is the rate of reaction defined as?

  The rate of reaction is the change in a quantity divided by time.
• What quantities can be used to measure the rate of reaction?

  • Mass of reactant used
  • Volume of gas formed
• What effect does increasing temperature have on the rate of reaction?

  It increases the rate of reaction because particles collide more frequently and with more energy.
• What are the three factors that increase the rate of reaction?

  1. Increasing the concentration of reactants in solution
  2. Increasing the pressure of gas reactants
  3. Increasing the surface area of solid reactants
• How do increasing concentration, pressure, and surface area affect the rate of reaction?

  They all increase the rate of reaction by making the reacting particles collide more frequently.
• What are the effects of adding a catalyst on the rate of reaction?

  A catalyst reduces the activation energy needed, making particles more likely to collide successfully and react. Catalysts are not used up in the reaction.
• What defines a reversible reaction?

  The products can return to their original reactants.
• What happens in a reversible reaction at equilibrium in a closed system?

  • The rates of the forward and reverse reactions become equal.
  • There is no more overall change in the quantities of reactants and products.
• What does Le Chatelier's principle state?

  If a system at equilibrium is subjected to a change, the system will adjust to counteract that change.
• How does pressure affect a reversible reaction at equilibrium?

  • Increasing pressure favors the reaction with fewer moles of gas.
  • Decreasing pressure favors the reaction with more moles of gas.
• How does changing the concentration of reactants affect equilibrium?

  • Removing molecules from one side shifts equilibrium in that direction, producing more on the reduced side.
  • Adding molecules to one side shifts equilibrium in the opposite direction, producing more on the added side.
• How does increasing temperature affect an endothermic reaction at equilibrium?

  It favors the endothermic reaction by shifting equilibrium towards the reverse reaction.
• How does decreasing temperature affect an exothermic reaction at equilibrium?

  It favors the exothermic reaction by shifting equilibrium towards the forward reaction.
• In a reversible reaction, if the forward reaction is exothermic, what can you conclude about the reverse reaction?

  The reverse reaction must be endothermic.
• What defines organic compounds?

  Organic compounds are those that have carbon forming the backbone of the molecules.
• Where is crude oil found?

  Crude oil is found underground.
• What is crude oil the result of?

  The burial of plankton under water a long time ago.
• What are hydrocarbons?

  Hydrocarbons are molecules consisting only of carbon and hydrogen atoms.
• What are alkanes?

  • Chains of single covalent bonded carbon atoms
  • Surrounded by hydrogen atoms
  • Always twice as many hydrogens as carbons plus two more
• What is the general formula for alkanes?

  $C_n H_{2n+2}$
• List the first six alkane names and their corresponding carbon chain lengths.

  • Methane (1 carbon)
  • Ethane (2 carbons)
  • Propane (3 carbons)
  • Butane (4 carbons)
  • Pentane (5 carbons)
  • Hexane (6 carbons)
• What is the purpose of fractional distillation in the context of crude oil?

  It separates different length alkanes based on their boiling points.
• What are the fractions collected in a fractionating column?

  • Bimon (very longest alkanes)
  • LPG (liquefied petroleum gas, up to 4 carbons)
  • Petrol (up to 8 carbons)
  • Kerosene (up to 12 carbons)
  • Diesel oil (up to 16 carbons)
  • Heavy fuel oil (over 16 carbons)
• Why do longer alkanes have higher boiling points?

  They have stronger intermolecular forces that require more energy to overcome.
• What fraction remains as a gas at the top of the fractionating column?

  LPG (liquefied petroleum gas).
• How is LPG transported and stored?

  LPG is stored in pressurized containers to transport it as a liquid.
• What is the longest alkane in LPG?

  Butane (4 carbons long).
• What are the different fractions of alkanes and their applications?

  • Petrol: used in cars
  • Kerosene: used for jet fuel
  • Diesel oil: used in cars and lorries
  • Heavy fuel oil: used in large ships
• What are the products of complete combustion of alkanes?

  Carbon dioxide and water.
• How do the viscosity and flammability of alkane fractions vary with chain length?

  Longer fractions are more viscous and less flammable, shorter fractions are more flammable and less viscous.
• What are polymers and how can they be made from alkanes?

  Polymers are long-chain hydrocarbons made from monomers, typically alkenes rather than alkanes.
• What functional group defines an alken?

  A carbon-carbon double bond, $C=$$C.$
• What does it mean for a molecule to be unsaturated?

  The molecule contains double or triple bonds and can bond with more atoms.
• Are alkanes saturated or unsaturated?

  Alkanes are saturated.
• When bromine water is added to an alken, what color change indicates a reaction has occurred?

  The solution turns from orange to colorless.
• What product is formed when bromine reacts with ethene?

  1,2-dibromoethane.
• What functional group is added to an alken when water reacts with it?

  Hydroxyl group, $-OH.$
• What type of compound is formed when an alken reacts with water?

  An alcohol.
• What are the two main problems associated with crude oil?

  1. Higher demand for shorter alkanes
  2. Insufficient alkenes for polymer production