Paper 2

• What can chemical reactions occur at?

  Vastly different rates
• What is a significant factor in how fast chemical reactions proceed?

  The reactivity of chemicals
• What can be manipulated to speed up or slow down chemical reactions?

  Many variables
• What do reversible chemical reactions require to maximize yield?

  Establishing the effect of different variables
• Why is understanding energy changes important in chemical reactions?

  It helps maximize the yield of desired product
• Who determines the effect of different variables on reaction rate in industry?

  Chemists and chemical engineers
• What do chemists and chemical engineers optimize in their processes?

  Product yield and energy efficiency
• How can the rate of a chemical reaction be found?

  By measuring reactant used or product formed
• What is the formula for mean rate of reaction?

  $\text{mean rate of reaction} =$$\frac{\text{quantity of reactant used}}{\text{time taken}}$
• What units may be used for the rate of reaction?

  g/s or cm3/s
• What is the general formula for alkanes?

  CnH2n+2
• What are the first four members of the alkanes?

  Methane, ethane, propane, butane
• How can the quantity of reactant or product be measured?

  By mass in grams or volume in cm³
• What does increasing the concentration of reactants do to the rate of reaction?

  Increases the frequency of collisions
• What does activation energy refer to?

  The minimum energy required for a reaction
• What happens to the rate of reaction when temperature increases?

  It increases due to more energetic collisions
• What do catalysts do in chemical reactions?

  Change the rate without being used up
• What is the effect of catalysts on activation energy?

  They provide a pathway with lower activation energy

  
• What are reversible reactions?

  Reactions where products can form reactants
• What happens when conditions change in a reversible reaction?

  The direction of the reaction can change
• What is equilibrium in a reversible reaction?

  When forward and reverse reactions occur at the same rate
• What does Le Chatelier’s Principle predict?

  The system responds to counteract changes
• What happens if the concentration of a reactant is increased?

  More products will be formed until equilibrium
• What happens if the temperature of a system at equilibrium is increased?

  Relative amount of products increases for endothermic reactions
• What is the effect of increasing pressure on gaseous reactions at equilibrium?

  Shifts equilibrium towards the side with fewer molecules
• What is crude oil primarily made of?

  Hydrocarbons
• What is the general formula for hydrocarbons in crude oil?

  CnH2n+2
• What is fractional distillation used for?

  To separate hydrocarbons into fractions
• What properties of hydrocarbons depend on molecular size?

  Boiling point, viscosity, and flammability
• What is produced during the complete combustion of hydrocarbons?

  Carbon dioxide and water
• What is cracking in hydrocarbons?

  Breaking down hydrocarbons into smaller molecules
• What are alkenes?

  More reactive hydrocarbons than alkanes
• What color change occurs when bromine water reacts with an alkene?

  It turns from brown to colorless
• What are the factors affecting the rates of chemical reactions?

  • Concentration of reactants
  • Pressure of reacting gases
  • Surface area of solid reactants
  • Temperature
  • Presence of catalysts
• What are the steps involved in fractional distillation?

  1. Heating crude oil
  2. Evaporation of hydrocarbons
  3. Condensation of vapors
  4. Collection of fractions
• What are the properties of hydrocarbons that change with molecular size?

  • Boiling point increases
  • Viscosity increases
  • Flammability decreases
• What are the uses of alkenes?

  • Production of polymers
  • Synthesis of pharmaceuticals
  • Creation of detergents
• What is the significance of carbon compounds in organic chemistry?

  • Form chains and rings
  • Source of fuels and materials
  • Basis for life
• What can hydrocarbons be broken down into through cracking?

  Smaller, more useful molecules
• What are the two methods of cracking mentioned?

  Catalytic cracking and steam cracking