Rates of reactions

• How can units for rate of reactions of concentration be written?

  Moldm-3/s
• How is concentration written with brackets?


  Concentration [ ]
• How does changing the concentration effect the rate of reaction?

  Rate of reaction is proportional to the concentration of a particular reactant raised to a power
• What are the common orders of reaction?

  1st, 2nd, 0
• What is zero order?

  It is where the conc of a reactant has no effect on rate, this is due to any power of 0 equalling 1
• What is first order?

  It is when the rectant depends on the concentration raised to the power of one, so if the conc is doubled the rate increases by a factor of 2
• What is second order?

  It is where a reaction with respect to the rate depends on it's concentration to the power of 2, therefore if the concentration is doubled then the rate quadruples (2^2)
• What is the rate equation?

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

  k= rate constant

  A= concentration of A

  B= concentration of B

  m and n= orders
• How do you calculate the overall order of a reaction?

  m+n
• How do you calculate the units of K?

  1. Rearrange the equation to make k the subject
  2. Substitute units into the expression for k
  3. cancel common units and show the units on a single line
• What do the big numbers in reactions represent?

  The stochiometric ratio
• What is the reaction mechanism?

  Series of steps that make up an overall reaction is called the reaction mechanism
• What is the rate determining step?

  It is the slowest step in a sequence
• How can concentration time graphs be plotted?

  Continuous measurements taken during the course of a reaction
• What is a calorimeter?


  It measures the amount of light absorbed by a solution
• How can you determine orders of reactants in a reaction?

  Look at the shape of the graph
• What order is it on concentration time graph if it is a straight line with a negative gradient?

  It is a 0 order
• What order is it on a concentration time graph if it is a curve with a negative gradient?

  First order
• What is half-life?


  It is the time taken for half of the reactant to be used up
• How can you tell order from half-lifes?


  calculate sucessive half lifes, if they are the same then it is 1st order
• How can you calculate k for a first order reaction?

  Calculate rate constant from the rate i.e rate/conc

  Or use the half life formula
• What is the half life formula by which you can calculate rate?

  ln2/halflife
• How is 0 order represented on rate conc graph?

  Straight flat line
• How is 1st order represented on a rate conc graph?

  Straight line with a positive gradient
• How is 2nd order represented on a rate conc graph?

  Upward curve with an increasing gradient
• What is the arrhenius equation?

  k=Ae^-ea/RT
• How can arrhenius be represented in arrhenius form?

  lnk= -Ea/R 1/T + lnA

  y= m x + c