REACTION KINETICS

For a reaction to occur:

Activation Energy - The minimum energy required for a chemical reaction to start.

Figure 1. Endothermic Reaction Graph

Figure 2. Exothermic Reaction Graph

- The rate of reaction is always represented as a positive number.

- The rate of reaction is the increase or decrease in concentration of products or reactants per unit time.

Reaction rates are equal to the slope tangent to that point.
The reaction rate changes as the reaction proceeds if the rate is dependent on the concentration of products.

*Note that the mole ratio of NO to O2 is 2:1. This can also be seen through the slopes of the products in the graph on the right.

Figure 3. Concentration Vs. Time Graph

How to measure rate of reaction through physical changes:

At a controlled temperature:

Change in volume of gas produced (volume vs. time)
Change in mass (mass vs. time)
Coloriometry (Absorbance vs. time)
Change in concentration through titration (Using the quenching technique - stop reaction at intervals)
Change in conductivity (For reactions involving change in number of ions)
Clock reactions (to find average rate over time)

CATALYSTS

Increase the rate of reaction without undergoing chemical change
Provide an alternate pathway with lower activation energy for reaction to take place

Figure 4. A catalysed reaction

Maxwell - Boltzman Energy Distribution Curve

Figure 6. Change with increase in temperature

Figure 7. Effect of catalyst

Figure 5. Original curve