Chem 12- Unit 1: Reaction Kinetics

How can reaction rate be measured? (5)

• Mass Change

  • Electric balance + stop watch

• Temperature Change

  • Thermometer + stopwatch

• Colour Change

  • Spectrophotometer + stopwatch

• Pressure Change

  • Pressure gauge + stopwatch

  • Must be change in # of mol of gas

• pH Change

  • pH gauge + stopwatch

What reactions speed up after a slow start? (4)

• Exothermic

• Changes in SA

• Coatings on reactant surface

• Autocatalysis

What impacts reaction rate (7)

• Temperature

  • 10° increase = rxn rate x2

• Concentration

• Pressure

  • Equivalent to concentration ↑

• Nature of reactants

  • Ve- + electron shielding

• Surface Area

  • HETEROgenous ONLY

• Catalysts/inhibitors

  • C = fast

  • I = slows/stops

• Phase of reactants

  • Aqueous > liquids/gases > solids

    • KMT

What makes a collision effective? (2)

• Geometry/Orientation

  • Both molec needs to be oriented the same

    • Ex. Horizontal + horizontal

• Activation Energy

  • Molecs need to be fast enough to break bonds

Activation Energy (1)

• Minimum amount of energy for reaction to occur

How does increasing molarity affect reaction rate? (2)

• Probability of collisions = increases

• Amount of collisions = same

Why does increasing temperature affect reaction rate? (3)

• Average kinetic kJ = increases

• Amount of collisions = increases

• Speed of collisions = increases

Potential energy and bonds (3)

• e- in chem bonds, number + types of atoms in molecs

• Bonds break = increases

  • Needs energy to break

• Bonds form = decreases

  • Releases energy

Kinetic Energy (1)

• Movement of molec in a system

  • Affects temperature