Reaction Order Calculator
Free Reaction order Calculator for chemical kinetics. Enter variables to compute results with formulas and detailed steps.
Formula
n = ln(rate2/rate1) / ln([A]2/[A]1)
The reaction order n is found by comparing rates from two experiments where only one reactant concentration changes. Taking the natural log of the rate ratio divided by the natural log of the concentration ratio gives the order. The rate constant k is then found by substituting back into the rate law.
Frequently Asked Questions
What is reaction order in chemistry?
Reaction order describes how the rate of a chemical reaction depends on the concentration of a particular reactant. A first-order reaction rate doubles when the reactant concentration doubles, a second-order reaction rate quadruples when concentration doubles, and a zero-order reaction rate is independent of concentration. The overall reaction order is the sum of all individual orders. Reaction orders are determined experimentally using the method of initial rates or integrated rate law analysis.
Can reaction order be a fraction or negative?
Yes, reaction orders can be fractional, zero, or even negative. Fractional orders (like 0.5 or 1.5) often indicate complex reaction mechanisms with multiple elementary steps. Negative orders mean that increasing the concentration of a reactant actually slows the reaction, which can occur when a reactant inhibits a catalytic surface or competes for active sites. Zero-order reactions proceed at a constant rate regardless of concentration, commonly seen in enzyme-catalyzed reactions at saturation.
What are integrated rate laws and how do they relate to reaction order?
Integrated rate laws describe how concentration changes over time for each reaction order. For zero order: [A] = [A]0 - kt (linear in [A] vs t). For first order: ln[A] = ln[A]0 - kt (linear in ln[A] vs t). For second order: 1/[A] = 1/[A]0 + kt (linear in 1/[A] vs t). By plotting experimental data in these forms, the one that gives a straight line reveals the reaction order. The slope of the straight line gives the rate constant k.
What formula does Reaction Order Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.