Average Rate of Reaction Calculator
Calculate chemical kinetics based on concentration changes over time
What is the Rate of Reaction?
The rate of reaction is a measure of how quickly a chemical reaction occurs. It is defined as the change in concentration of a reactant or product over a specific period of time. In most laboratory settings, this is measured in moles per liter per second (mol/L·s).
The Rate Formula
The mathematical expression for the average rate of reaction is:
Rate = |(C₂ – C₁) / (t₂ – t₁)|
Where:
- C₁: Concentration at time t₁
- C₂: Concentration at time t₂
- t₁: Initial time
- t₂: Final time
Rate of Reaction Calculation Example
Suppose you are monitoring the decomposition of Hydrogen Peroxide (H₂O₂). At the start of the experiment (0 seconds), the concentration is 2.50 M. After 50 seconds, the concentration drops to 2.10 M. What is the average rate of reaction?
| Variable | Value |
|---|---|
| Initial Concentration (C₁) | 2.50 mol/L |
| Final Concentration (C₂) | 2.10 mol/L |
| Initial Time (t₁) | 0 s |
| Final Time (t₂) | 50 s |
| Calculation | (2.10 – 2.50) / (50 – 0) = -0.04 / 50 |
| Average Rate | 0.0008 mol/L·s |
Why do we use Absolute Values?
While the change in concentration for a reactant is negative (because it is being consumed), the rate of reaction is conventionally expressed as a positive value. This represents the speed of the process regardless of whether you are tracking the disappearance of a reactant or the appearance of a product.
Factors That Influence Reaction Rates
- Concentration: Higher concentrations usually lead to more frequent collisions between particles, increasing the rate.
- Temperature: Increasing temperature gives particles more kinetic energy, leading to more effective collisions.
- Surface Area: For solids, a finer powder reacts faster than a large block because more particles are exposed.
- Catalysts: These substances lower the activation energy required for a reaction to proceed without being consumed themselves.