Rate Constant Calculator Formula
Understand the math behind the rate constant calculator. Each variable explained with a worked example.
Formulas Used
Rate Constant (k)
k = a_factor * pow(e, -ea / (8.314 * temp))Variables
| Variable | Description | Default |
|---|---|---|
a_factor | Pre-exponential Factor (A) | 10000000000 |
ea | Activation Energy (Ea)(J/mol) | 50000 |
temp | Temperature (T)(K) | 298 |
How It Works
Arrhenius Equation
Formula
k = A × e^(−Ea / RT)
Where:
The rate constant increases exponentially with temperature and decreases with higher activation energy.
Worked Example
A = 1 × 10¹⁰, Ea = 50,000 J/mol, T = 298 K.
a_factor = 10000000000ea = 50000temp = 298
- 01k = A × e^(-Ea/RT)
- 02k = 1×10¹⁰ × e^(-50000/(8.314×298))
- 03k = 1×10¹⁰ × e^(-20.18)
- 04k = 1×10¹⁰ × 1.71×10⁻⁹
- 05k = 17.1
Frequently Asked Questions
What is the pre-exponential factor?
A (also called the frequency factor) relates to the frequency of molecular collisions and the probability that they have the correct orientation for reaction.
What units does k have?
The units depend on reaction order: zero order = M/s, first order = 1/s, second order = 1/(M·s).
How does doubling temperature affect k?
A rough rule is that k doubles for every 10 K increase near room temperature, but the actual effect depends on Ea.
Ready to run the numbers?
Open Rate Constant Calculator