Chemical Reaction Rate Calculator
Average Rate of Reaction
0 M/s
How to Calculate Rate of Reaction Given Time and Concentration
In chemical kinetics, the rate of reaction is defined as the speed at which reactants are converted into products. It is quantified by measuring the change in concentration of a reactant or product over a specific time interval. Understanding this calculation is fundamental for chemists and students analyzing reaction speeds.
Rate = Δ[Concentration] / ΔTime
The Formula Explained
The average rate of reaction can be calculated using the formula above, where:
- Δ[Concentration] represents the change in molarity (Final Concentration – Initial Concentration).
- ΔTime represents the time interval over which the change occurred.
Units are typically expressed as Molarity per second (M/s) or mol·L⁻¹·s⁻¹.
Reactants vs. Products
When measuring the rate based on a reactant, the concentration decreases over time, resulting in a negative value mathematically. However, reaction rates are conventionally reported as positive values. Therefore, for reactants:
Rate of Disappearance = – (Δ[Reactant] / Δt)
When measuring based on a product, the concentration increases, resulting in a positive value:
Rate of Appearance = + (Δ[Product] / Δt)
Example Calculation
Suppose you start a reaction with a concentration of reactant A at 0.50 M. After 20 seconds, the concentration drops to 0.10 M.
- Calculate the change in concentration: 0.10 M – 0.50 M = -0.40 M.
- Identify the time interval: 20 seconds.
- Apply the formula: Rate = -0.40 M / 20 s = -0.02 M/s.
Since reaction rates are positive magnitudes, the rate of disappearance of A is 0.02 M/s.
Factors Affecting Reaction Rate
Several variables influence how fast a chemical reaction proceeds:
- Concentration: Higher concentrations usually increase the collision frequency between particles.
- Temperature: Higher temperatures increase kinetic energy, leading to more frequent and energetic collisions.
- Surface Area: For solids, a larger surface area allows more reactant particles to interact.
- Catalysts: These substances lower the activation energy required for the reaction to occur.