A Level Chemistry

• What is the definition of the rate of a chemical reaction?

  Change in concentration per unit time
• How does changing the concentration of reactants affect the rate of reaction?

  It usually changes the rate of reaction
• What does a rate equation show?

  The effect of concentration on reaction rate

  
• Can the rate equation be determined from the stoichiometric equation?

  No, it must be determined experimentally
• What is the general form of the rate equation for a reaction A + B → products?

  Rate = k[A]^m[B]^n

  
• What does 'k' represent in the rate equation?

  Rate constant

  
• What do [A] and [B] represent in the rate equation?

  Concentrations of reactants A and B

  
• What do 'm' and 'n' represent in the rate equation?

  Order of reaction with respect to A and B

  
• How are the orders of reaction determined?

  They can only be determined experimentally

  
• What are the possible orders of reaction?

  Zero, first, or second
• How does temperature affect the rate constant (k)?

  Rate constants are temperature dependent
• What is the overall order of a chemical reaction?

  Sum of individual orders of reaction

  
• What happens to the rate when the concentration of I- or H+ is doubled?

  The rate increases by a factor of 4

  
• What happens to the rate when the concentration of IO3- is doubled?

  The rate doubles
• What is the order with respect to iodide?

  2
• What is the order with respect to iodate?

  1
• What is the order with respect to hydrogen ions?

  2
• What is the overall order of the reaction?

  5
• What happens to the initial rate of reaction when the concentration of H2 is tripled?

  • Rate triples
• What happens to the initial rate of reaction when both H2 and ICl concentrations are doubled?

  • Rate quadruples

  
• How can the initial rate of reaction be deduced from a tangent at t=0?

  By drawing a tangent to the curve
• What is the rate equation when the initial concentration of A is doubled and the rate increases by a factor of 4?

  Rate = k[A]^2[B]

  
• How do we determine the rate equation using the initial rates method?

  • Alter concentration of one reactant
  • Measure effect on initial rate
  • Use known concentrations at the start

  
• What does an order of 0 mean in terms of concentration effect on rate?

  Rate is not affected by a change in [A]

  
• What does an order of 1 mean in terms of concentration effect on rate?

  Rate is proportional to [B]

  
• What does an order of 2 mean in terms of concentration effect on rate?

  Rate is proportional to [C]^2

  
• What is the process for calculating the order of reaction with respect to A and B?

  • Keep A constant, vary B
  • Keep B constant, vary A
  • Examine data to calculate orders

  
• What is the rate equation derived from the provided experimental data?

  Rate = k[A][B]^2

  
• How do we calculate k and deduce the units from the overall order of reaction?

  • Zero: Rate = k[A]^0
  • First: Rate = k[A]
  • Second: Rate = k[A][B]
  • Third: Rate = k[A]^2[B]
  • Fourth: Rate = k[A]^2[B]^2

  
• What is the initial rate of disappearance of NO in the first experiment?

  0.7 x 10^-4 moldm-3s-1
• What is the initial rate of disappearance of NO in the second experiment?

  2.8 x 10^-4 moldm-3s-1
• What is the initial rate of disappearance of NO in the third experiment?

  18.9 x 10^-4 moldm-3s-1
• How can we calculate the rate of reaction using concentration-time graphs?

  • Measure increase in product concentration
  • Measure decrease in reactant concentration
  • Plot concentration changes over time

  
• What are methods of continuous monitoring for reaction rates?

  • Collecting gas produced
  • Measuring mass lost
  • Observing color change with colorimeter
• What is the purpose of a calibration plot in colorimetry?

  To determine concentration from absorbance
• What is the reaction that produces a Fe2+ solution?

  Fe + 2 HCl → FeCl2 + H2
• What are suitable methods for monitoring various reactions?

  • Mass change
  • Gas collection
  • Colorimetry
• What happens to the rate of reaction over time according to collision theory?

  Rate decreases as reactants are consumed
• What physical property changes in a precipitation reaction?

  Electrical conductivity decreases over time
• What is the formula for calculating the rate of a chemical reaction?

  Rate = Change in concentration / Time