Reaction Order Determiner | Online Free Tool | Elysia Tools
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Reaction Order Determiner
Initial-rate method: single-reactant log-log fit or two-reactant method of pairs, with k back-calculated per experiment.
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Tool usage guide
Learn when to use this tool, what it supports, and how real users apply it.
Key facts
Category
Science & Education
Input types
textarea
Output type
text
Sample coverage
4
API ready
Yes
Overview
The Reaction Order Determiner calculates individual reaction orders, the overall rate law, and the apparent rate constant from experimental initial-rate data. It supports single-reactant systems using log-log linear regression and two-reactant systems using the classic method of pairs, automatically back-calculating rate constants for each trial.
When to use
Analyzing chemical kinetics lab data where initial reaction rates are measured across varying reactant concentrations.
Determining whether a single-reactant process follows zero, first, second, or fractional order kinetics.
Solving multi-reactant rate law problems using isolation or method of pairs comparison.
How it works
1Enter experimental initial-rate data into the text area with one trial per line, formatting as '[A] rate' for single reactants or '[A] [B] rate' for two reactants.
2For single-reactant sets, the tool runs a least-squares log-log linear regression (ln v₀ = n·ln[A] + ln k) to extract the reactant order and baseline rate constant.
3For two-reactant sets, the tool isolates pairs where one reactant is held constant to determine individual partial orders (n_A and n_B) using logarithmic rate-to-concentration ratios.
4The tool formats the final rate law equation, back-calculates the rate constant k for each individual trial, and outputs the average k value.
Use cases
Undergraduate and high school chemistry students verifying rate law calculations from kinetic laboratory reports.
Chemistry instructors creating and checking problem sets for the method of initial rates.
Chemical researchers estimating empirical reaction orders and rate constants from bench-scale kinetic screening.
Examples
1. Single-Reactant Decomposition
Chemistry Student
Background
A student measures the decomposition rate of nitrogen dioxide at three starting concentrations in a kinetics lab.
Problem
The student needs to determine if NO2 decomposition is first or second order and find the average rate constant.
How to use
Enter the concentration and rate pairs line-by-line into the experiment input field.
0.10 0.02
0.20 0.08
0.40 0.32
Outcome
The tool performs a log-log fit showing order n_A = 2, rate law v = k·[A]^2, and an average k of 2.
2. Two-Reactant Reaction Order Determination
Lab Instructor
Background
An instructor needs to verify exam solution keys for an initial-rate problem involving reactants A and B.
Problem
Calculate individual orders n_A and n_B, overall reaction order, and rate constant k across three experimental runs.
How to use
Paste three trials containing [A], [B], and initial rate values into the tool.
FAQ
What input format does the tool expect?
Enter whitespace-separated values on each line: use two values '[A] rate' for a single reactant, or three values '[A] [B] rate' for two reactants.
Can I use scientific notation for small reaction rates?
Yes, standard scientific notation like 2.0e-3 or 4.0e-4 is fully supported for concentrations and rates.
How does the tool identify integer reaction orders?
Calculated orders within 0.05 of a whole number are recognized as clean integer orders (such as 0, 1, 2, or 3).
How is the rate constant k calculated?
The rate constant k is computed individually for every experiment by substituting measured concentrations and rates into the derived rate law, then averaged across all trials.
What happens if a two-reactant dataset lacks matching pairs?
The two-reactant method requires pairs where one concentration is held constant to isolate individual partial orders.
The tool identifies n_A = 1 from fixed [B] pairs and n_B = 2 from fixed [A] pairs, yielding rate law v = k·[A][B]^2, overall order 3, and average k = 2.0.