Notes on Rates of Reactions

Methods of Measuring Reaction Rates:
1. Collecting Gas Produced:
- Measure the volume of gas produced.
- Suitable for reactions that give off gas.
1. Displacement of Water:
- Use a gas syringe to collect gas produced, especially for non-soluble gases.
1. Measuring Loss of Mass:
- Monitor the decrease in mass of reactants at regular intervals.
Graphing Results:
- Once data is collected, plot on a graph to visualize reaction progress.

Increasing Reaction Rates:
- Temperature:
  - Higher temperatures increase kinetic energy and frequency of collisions.
- Concentration of Reactants:
  - A higher concentration leads to more effective collisions between molecules.
- Surface Area:
  - Increasing surface area (e.g. by grinding solids) allows more particles to collide quicker.
- Catalysts:
  - Catalysts speed up reactions without being consumed, remaining chemically unchanged after the reaction.
State Symbols:
- (s) = solid
- (g) = gas
- (l) = liquid
- (aq) = aqueous solution

Changing the quantity of reactants affects the amount of product generated.
- Example:
  - Using 10g of calcium carbonate in a reaction produces a certain amount of product.
  - If only 5g is used, the maximum product generated will be halved.

Average Rate Calculation:
- Since rates change over time, average rate over a period is measured.
- Formula:
  Rate = \frac{\Delta \text{quantity}}{\Delta \text{time}}
- Example Calculation:
- Change in concentration over 20 seconds.
- Initial concentration = 0.12 M, final concentration = 0.24 M.
- Calculating average rate:
  Rate = \frac{0.24 - 0.12}{20} = 0.006 \text{ M s}^{-1}
- Units:
- Concentration in molarity (M), time in seconds (s), hence rate in M s^-1.

The average rate of reaction decreases as reactant particles are consumed, leading to fewer effective collisions as time progresses.