kinetics

• Rate of chemical reactions

  Measures the change in concentration of reactant or the change in concentration of product with time
• Rate of reaction


  How fast the given reaction is taking place
• Rate


  Change in concentration of reactants or change in concentration of product with respect to time
• Rate can be expressed in terms of reactant or product
• Reaction A is converted into B

  1. Decrease in concentration of A

  2. Increase in concentration of B
• Reaction rate


  How fast a given reactant is converted into a given product
• Reaction progress can be monitored by decrease in reactant concentration or increase in product concentration
• Coefficients of balanced chemical equation are used in rate expressions
• Rate of reaction

  How fast a given reaction is taking place
• Determining rate of reaction


  • Measuring change in observable properties over time
  • Could be color change, temperature change, appearance of new substance, etc.
• Determining rate of reaction

  1. Measure change in concentration over time

  2. Change in n2o5 over change in time = 1/4 * change in o2 over change in time
• Reaction rate expression

  Any change in observable property that indicates how fast the given reaction is taking place
• Determining change in concentration over time

  1. Measure increase in pressure

  2. Measure intensity of brown color due to no2 formation
• Absorbance

  Directly proportional to concentration
• Rate of reaction can be determined by measuring change in volume, temperature, or pressure
• Experiment


  • Thermal decomposition of n2o5 at 55°C
• Initial concentration of n2o5 is 0.02 mol/L
• After 100 seconds, concentration of n2o5 is 0.169 mol/L
• After 100 seconds, concentration of no2 is 0.63 mol/L and concentration of o2 is 0.115 mol/L
• Calculating rate of formation of o2

  1. Change in concentration of o2 over change in time

  2. Final concentration - initial concentration / final time - initial time
• Rate of formation of o2 is 3.7 x 10^-5 mol/L/s
• Calculating rate of disappearance of n2o5

  1. Change in concentration of n2o5 over change in time

  2. Initial concentration - final concentration / final time - initial time
• Rate of disappearance of n2o5 is 1.9 x 10^-5 mol/L/s
• Calculating rate of formation of no2


  1. Change in concentration of no2 over change in time

  2. Final concentration - initial concentration / final time - initial time
• Rate of formation of no2 is 2.2 x 10^-5 mol/L/s
• The reaction is: n2o5 -> no2 + o2
• Initial concentration of n2o5 is 2 x 10^-2 mol/L
• Concentration of no2 produced is 0.8 x 10^-2 mol/L
• Concentration of o2 produced is 0.4 x 10^-2 mol/L