Chemical Kinetics Notes

Physical State of Reactants:
- Molecules must come into contact to react.
- Reaction rates: gas > liquid (solution) > solid.
- Solids are often dissolved in a solvent to create a solution before reacting.
Concentration of Reactants:
- Increased concentration leads to more collisions and a higher reaction rate.
Temperature:
- Higher temperatures increase kinetic energy, leading to faster movement, more frequent collisions, and greater collision energy.
Catalyst or Inhibitor:
- A catalyst speeds up a reaction without being consumed.
- An inhibitor slows down a reaction without being consumed.

Reaction rate is the change in concentration of reactants or products per unit of time.
Common unit: M s-1 (mol L-1 s-1).
Reaction rates are always positive (or zero).
Rate = $± \frac{∆[X]}{∆t}$ where:
- "+" if X = reaction product, because ∆[X] > 0
- "-" if X = reagent, because ∆[X] < 0
- ∆t > 0 always

Average Rate:
- The average rate of the reaction over each interval is the change in concentration divided by the change in time: Average rate = \frac{[C4H9Cl]}{t}
Instantaneous Rate:
- The slope of a line tangent to the curve (concentration vs. time plot) at any point is the instantaneous rate at that time.
- Instantaneous rate = $- \frac{d[A]}{dt}$

For the reaction: aA + bB → cC + dD
- Rate = -\frac{1}{a} \frac{[A]}{t} = -\frac{1}{b} \frac{[B]}{t} = \frac{1}{c} \frac{[C]}{t} = \frac{1}{d} \frac{[D]}{t}