18.2 Concentration-time graphs

• The half-life of a reactant is the time for its concentration to decrease by half
• A first order reaction has a constant half-life
• To find the rate using a concentration-time graph

  • draw a tangent to the curve at that time
  • measure the gradient of the tangent
• For a first order reaction, the rate constant k can be determined from the constant half-life

  k = ln2 / half-life