Reaction order from rate data calculator
If doubling the concentration from 0.1 to 0.2 raises the initial rate from 0.01 to 0.04, the reaction is second order in that reactant. Enter the two rates and the two matching concentrations to get the order n. Free in your browser.
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- Your data stays on your device
Run — free
Worked example
- Rate1
- 0.04
- Rate2
- 0.01
- Concentration1
- 0.2
- Concentration2
- 0.1
- Order
- 2
- Rate ratio
- 4
- Concentration ratio
- 2
- Nearest integer order
- 2
This reaction order from rate data calculator finds the reaction order n with respect to one reactant from two initial-rate experiments. Enter rate1 and rate2 together with the corresponding concentrations of the reactant you varied; the engine returns n from the classical method-of-initial-rates identity n equals log of the rate ratio over log of the concentration ratio. When concentration doubles and the rate quadruples, the order is two; when rate scales one-to-one with concentration, the order is one; a rate that does not change with concentration is zero order. The path is fully deterministic floating-point arithmetic with no network calls, no sampling, and no date-dependent shortcuts. Equal concentrations are rejected because the log concentration ratio would be zero and the order cannot be determined.
What two experiments reveal about the order
In elementary kinetics teaching, the rate law for a single reactant of interest is often written rate equals k times concentration of A to the power n. When two carefully designed initial-rate experiments keep temperature and other species fixed and change only the concentration of A, the unknown rate constant cancels in the ratio of the two rates. That leaves rate1 over rate2 equals the concentration ratio raised to n, which rearranges to n equals the logarithm of the rate ratio divided by the logarithm of the concentration ratio.
Any positive log base works because the base cancels; this calculator uses natural logs internally and reports a stable floating-point order.
Where order-from-rates fits in study, labs, and software
Students meet the method of initial rates when a textbook table lists two or more experiments with different starting concentrations and measured initial rates, and the task is to read off the order with respect to one reactant. Teachers can pre-generate answer keys for clean integer orders and for slightly noisy non-integer floats without trusting opaque apps that silently round or switch log bases.
Developers call the same contract from scripts to seed deterministic test vectors for kinetics trainers, to normalize lab-imported pairs before plotting log-log slopes, or to satisfy programming-challenge statements that demand n rather than a hand-waved guess. Contest practice often needs a fast offline source of orders so solutions can be checked without graphing calculators under time pressure. Product and education tools use the identity when a learner types two rates and two concentrations and the UI must show whether the reaction is zero, first, or second order in that species.
What you can do with it
Homework and kinetics drills
Find the order n from textbook two-experiment tables and verify first-, second-, or zero-order conclusions before writing the full rate law.
Lab report checks
Turn two measured initial rates and the matching reactant concentrations into a reproducible order for lab write-ups and answer keys.
FAQ
What does the reaction order from rate data calculator cost?
It is free in your browser on this page.
How is the reaction order defined here?
For rate = k[A]^n from two experiments, n = log(rate1/rate2) / log(concentration1/concentration2). Any positive log base is equivalent because the base cancels.
What happens if the two concentrations are equal?
Equal concentrations make log(conc1/conc2) zero, so the order cannot be determined from those two experiments alone.
Can rates or concentrations be zero or negative?
No. Both rates and both concentrations must be strictly positive finite numbers so the log ratios are defined for this elementary method.
Does this fit a full multi-reactant rate law?
No. It only computes the order with respect to one reactant from two rate–concentration pairs for that species. Use dedicated tools if you need multi-species fitting.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/chem/reaction-order-from-rates \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"rate1":0.04,"rate2":0.01,"concentration1":0.2,"concentration2":0.1}'const res = await fetch("https://api.kit.forhosting.com/chem/reaction-order-from-rates", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"rate1": 0.04,
"rate2": 0.01,
"concentration1": 0.2,
"concentration2": 0.1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/reaction-order-from-rates",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"rate1": 0.04,
"rate2": 0.01,
"concentration1": 0.2,
"concentration2": 0.1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/reaction-order-from-rates", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"rate1":0.04,"rate2":0.01,"concentration1":0.2,"concentration2":0.1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"rate1":0.04,"rate2":0.01,"concentration1":0.2,"concentration2":0.1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/reaction-order-from-rates", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"rate1": 0.04,
"rate2": 0.01,
"concentration1": 0.2,
"concentration2": 0.1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.reaction_order_from_rates",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_abs_value | 1000000000000000 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
What reaction order from two experiments means and what the response contains
The response includes the normalized rate1, rate2, concentration1, and concentration2, the computed order, the rate_ratio and concentration_ratio used in the formula, a nearest_integer_order helper for textbook answers that expect 0, 1, or 2, an is_integer_order flag when the floating-point result is within rounding tolerance of that integer, the method tag method_of_initial_rates, the precision used, and a short formula string. There is no black-box regression over many points and no symbolic CAS path: the engine either evaluates the closed-form ratio identity inside the supported magnitude range or rejects the input with invalid_input. Rejected cases include missing fields, non-finite values, non-positive rates or concentrations, magnitudes above the documented ceiling, and any pair where concentration1 equals concentration2, because then the denominator log of the concentration ratio is zero and the order is undefined from those two trials alone.
How rates and concentrations are read and how the order stays reproducible
Optional leading plus signs and scientific notation on numeric strings are allowed when they parse as finite decimals; embedded spaces, hex prefixes, and non-numeric tokens are rejected with a clear message so a bad cell does not become a wrong order. Both rates and both concentrations must be strictly positive: zero or negative values make the log ratios undefined for real numbers in this elementary setting. The preferred fields are rate1 and rate2 for the two measured initial rates in consistent units such as moles per liter per second, and concentration1 and concentration2 for the reactant levels in those same two experiments. Concentrations must differ; if they are equal within a tight relative tolerance the request fails with invalid_input naming that concentrations must not be equal. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for the numeric fields, defaulting to ten and capped at fifteen so JSON goldens stay stable.
Where order-from-rates fits in study, labs, and software
On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the KIT tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the mathematical result. Pair it with Arrhenius or half-life tools when you need related kinetics steps, and with other chem endpoints when you are building a small lab of free, deterministic physical-chemistry helpers.
Integration use cases
Deterministic test fixtures
Generate stable order, ratio, and nearest-integer fields for unit tests, tutoring apps, and CI assertions without re-deriving log ratios by hand.