Equilibrium constant from Gibbs calculator
Turn a standard Gibbs energy change into an equilibrium constant: −10,000 J/mol at 298.15 K gives K above one, so products are favored, while a ΔG° of zero gives exactly one. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Delta g
- -10,000
- Creativity
- 298.15
- Gas constant
- 8.314
- K
- 56.4965185085
- Ln K
- 4.0341790169
- Log10 K
- 1.7520216861
This equilibrium constant from Gibbs calculator evaluates the standard thermodynamic identity K equals exp of minus ΔG° over R times T for a chemical reaction at a stated absolute temperature. You supply the standard Gibbs free energy change ΔG° and the temperature T in kelvin; the engine returns the dimensionless equilibrium constant K, the natural logarithm ln(K), the common logarithm log10(K), and a clear favor label so you can see whether products or reactants dominate at equilibrium. The arithmetic is fully deterministic: one division and one exponential on finite numbers, with no network calls, no formation-table lookups, and no date-dependent shortcuts. Keep energy units consistent before you call—if ΔG° is in joules per mole, leave the default gas constant R at 8.314 joules per mole-kelvin; if ΔG° is in kilojoules per mole, set R to 0.008314.
What the equilibrium constant tells you
The thermodynamic equilibrium constant K quantifies how far a reaction lies toward products or reactants when the system has reached equilibrium under standard activity conventions. The closed form that links free energy to that constant is ΔG° equals minus R T times the natural logarithm of K, which rearranges to K equals exp of minus ΔG° over R times T. A large K means the equilibrium mixture is rich in products; a small K means reactants dominate; K near one marks a balanced mixture.
This calculator implements that closed form only.
Where K from ΔG° fits in study, lab work, and software
Students meet the link between Gibbs free energy and the equilibrium constant when a general-chemistry unit moves from spontaneity tables to quantitative K values, when a physical-chemistry course derives ΔG° equals minus R T ln K from chemical potential, or when an exam problem asks for K at a stated temperature given a tabulated free-energy change. Teachers can pre-generate answer keys for modest ΔG° and T values without trusting opaque calculator apps that silently switch from joules to kilojoules and invert the exponent sign.
Developers call the same contract from scripts to seed deterministic test vectors for thermo dashboards, to normalize user-entered reaction parameters before process demos, or to satisfy programming-challenge statements that demand K rather than a hand-waved large or small label. Lab and process work often needs a fast, offline source of equilibrium-constant checks so report numbers can be verified against the stated formula under time pressure.
Product and education tools use the evaluation when a learner types free energy and temperature and the UI must show K plus a clear products-favored or reactants-favored label.
What you can do with it
Homework and exam K from ΔG° drills
Plug textbook standard free-energy changes and kelvin temperatures into K = exp(−ΔG°/RT) and check whether products or reactants are favored.
Lab reports and tutoring software
Normalize user-entered ΔG° and temperature into equilibrium constants for worksheets, plotters, and interactive thermo lessons.
FAQ
What does the equilibrium constant from Gibbs calculator cost?
It is free in your browser on this page.
How is K defined from ΔG°?
K = exp(−ΔG°/(R·T)), where ΔG° is the standard Gibbs free energy change, T is absolute temperature in kelvin, and R is the gas constant in energy units matching ΔG°. Keep units consistent across ΔG° and R.
What happens if temperature is zero or negative?
Zero or negative absolute temperature is non-physical here because the formula divides by T.
Does this tool compute ΔG° from enthalpy and entropy?
No. You must supply ΔG° yourself. Use a Gibbs free energy calculator for ΔG = ΔH − TΔS if you only have enthalpy and entropy, then pass that ΔG° here.
Why are results rounded to a precision?
Default precision is 10 decimal places; you can set precision from 0 to 15.
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/equilibrium-from-gibbs \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"delta_g":-10000,"temperature":298.15}'const res = await fetch("https://api.kit.forhosting.com/chem/equilibrium-from-gibbs", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"delta_g": -10000,
"temperature": 298.15
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/equilibrium-from-gibbs",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"delta_g": -10000,
"temperature": 298.15
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/equilibrium-from-gibbs", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"delta_g":-10000,"temperature":298.15}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"delta_g":-10000,"temperature":298.15}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/equilibrium-from-gibbs", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"delta_g": -10000,
"temperature": 298.15
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.equilibrium_from_gibbs",
"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 the equilibrium constant means and what the response contains
It returns the normalized delta_g, temperature, and gas_constant you supplied, the equilibrium constant K rounded to the requested precision, ln_K and log10_K for log-scale work and van't Hoff style checks, a string favor tag of products, reactants, or equilibrium, a boolean products_favored flag that is true when ΔG° is negative, false when positive, and null when the result is at equilibrium within a tiny numeric epsilon, the precision used, the method tag equilibrium_from_gibbs, the formula string K equals exp of minus ΔG° over R T, and a short unit_note reminding you to keep energy scales consistent between ΔG° and R. There is no approximate CAS path and no random sampling of conditions: the engine either builds a finite or representable K inside the supported magnitude range or rejects the input with invalid_input. Rejected cases include missing delta_g or temperature, non-finite values, magnitudes above the documented ceiling, a gas constant of zero, and any temperature that is zero or strictly negative on the absolute kelvin scale.
How ΔG°, temperature, and R are read and stay 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 equilibrium constant. Zero ΔG° is valid and yields K equal to one. The preferred fields are delta_g for the standard free-energy change and temperature for absolute T in kelvin, but aliases such as gibbs, dG, deltaG, and gibbs_energy for ΔG°, and T, temp, kelvin, temp_k, and absolute_temperature for temperature are accepted so spreadsheets, query strings, and typed forms can reuse the same contract. Optional gas_constant defaults to 8.314 joules per mole-kelvin when omitted; aliases R, r, and gasConstant let you pass a matching R when ΔG° is in kilojoules or calories. Temperature must be strictly positive: if T is zero or less than zero, the request fails with invalid_input because division by T is undefined and negative absolute temperature is non-physical for this relation. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for all finite numeric fields, defaulting to ten and capped at fifteen so JSON goldens stay stable. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing the equilibrium formula yourself.
Where K from ΔG° fits in study, lab work, 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 the Gibbs-from-enthalpy-entropy helper when you need ΔG first, and with other chemistry endpoints when you are building a small lab of free, deterministic reaction helpers.
Integration use cases
Deterministic test fixtures
Generate reproducible K, ln_K, log10_K, and favor labels for unit tests, property checks, and CI assertions.