The reaction rate is measured by tracking how fast the concentration of reactants decreases or products increase over time.
Methods of measurement:
- Change in concentration:
- Measure how the amount of reactant or product changes over a certain time interval using chemical analysis.
- Units: mol L⁻¹ s⁻¹
- Gas volume measurement:
- For reactions producing a gas, measure the volume of gas evolved over time.
- Example: Using a gas syringe or water displacement.
- Mass change:
- For reactions producing or consuming solids/gases, measure the change in mass over time.
- Example: Magnesium reacting with acid loses mass as hydrogen gas forms.
- Color change / spectrophotometry:
- For colored reactants/products, use a spectrophotometer to measure absorbance change over time.
- Change in pressure:
- For gaseous reactions, track pressure changes in a closed container.
In short: Reaction rate is measured by monitoring a property that changes as the reaction proceeds—concentration, volume, mass, color, or pressure—per unit time.