Le Chatelier pressure shift calculator
See which way an equilibrium moves when you raise the pressure: ammonia synthesis has 4 moles of gas on the reactant side and 2 on the product side, so it shifts toward the products, the side with fewer gas moles. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Moles reactants
- 2
- Moles products
- 1
- Delta n gas
- -1
- Fewer moles side
- products
- Direction
- forward
- Shift
- toward_products
This Le Chatelier pressure shift calculator predicts how a chemical equilibrium moves when total pressure increases at constant temperature, using only the moles of gas on each side of a balanced equation. According to Le Chatelier’s principle, increasing pressure favors the side with fewer moles of gas, because that composition reduces the system’s volume response. You enter the stoichiometric gas totals for reactants and products; the engine compares them and returns a clear shift direction—toward reactants or toward products—plus delta n of gas and readable tags for reverse or forward net reaction. Equal gas mole counts are rejected, because pressure then has no preferred side under the ideal-gas rule. Classic checks include ammonia synthesis (four gas moles of reactants versus two of product) shifting toward products, and phosphorus pentachloride dissociation (one mole versus two) shifting toward reactants. The path is fully deterministic arithmetic with no network calls, no sampling, and no date-dependent shortcuts.
What Le Chatelier predicts when pressure increases
Le Chatelier’s principle states that a system at equilibrium responds to a disturbance by shifting in the direction that partially counters that disturbance. For an ideal-gas mixture at fixed temperature, raising total pressure—typically by reducing volume—increases the number of molecular collisions per unit volume. The equilibrium composition that lowers the total number of gas particles is then favored, so the reaction net-moves toward the side with fewer moles of gas.
Only gaseous stoichiometric coefficients enter the count: solids and pure liquids do not contribute gas moles and are omitted by the caller. This calculator does not solve for equilibrium constants or partial pressures; it only classifies the qualitative pressure-driven shift from the two side totals.
Where pressure-shift checks fit in study, lab, and software
Students meet pressure effects when textbooks treat ammonia synthesis, Haber–Bosch yield under high pressure, or gas-phase dissociations such as dinitrogen tetroxide to nitrogen dioxide. Teachers can pre-generate answer keys for modest coefficient sets without relying on opaque calculator apps that mix temperature and concentration rules into one confusing screen. Developers call the same contract from scripts to seed deterministic test vectors for equilibrium tutors, to normalize user-entered reaction tables before a demo, or to satisfy programming-challenge statements that demand a shift tag rather than a hand-waved explanation.
Contest practice often needs a fast, offline source of direction labels so solutions can be checked without graphing calculators under time pressure. Product and education tools use the classifier when a learner types gas moles on each side and the UI must show whether increasing pressure favors reactants or products.
What you can do with it
Homework and pressure-effect checks
Enter gas moles on each side of a balanced equation and verify whether increasing pressure favors reactants or products before lab or exam work.
Teaching demos and reaction tables
Normalize user-entered gaseous stoichiometry into clear forward/reverse pressure-shift labels for interactive lessons and dashboards.
FAQ
What does the Le Chatelier pressure shift calculator cost?
It is free in your browser on this page.
Which way does equilibrium shift when pressure increases?
Toward the side with fewer moles of gas. If reactant gas moles are smaller, the shift is reverse (toward reactants); if product gas moles are smaller, the shift is forward (toward products).
What happens if both sides have the same number of gas moles?
Equal gas mole totals mean an increase in pressure does not favor either side under this ideal-gas rule.
Do solids and liquids count in the mole totals?
No. Only gaseous species stoichiometric coefficients should be summed. Solids and pure liquids contribute zero gas moles and should be left out of your inputs.
Does this tool compute K or equilibrium composition?
No. It only classifies the qualitative pressure-increase shift from the two gas mole totals. Use a dedicated equilibrium constant or Q-versus-K tool for quantitative direction from concentrations or pressures.
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/le-chatelier-pressure-shift \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"moles_reactants":2,"moles_products":1}'const res = await fetch("https://api.kit.forhosting.com/chem/le-chatelier-pressure-shift", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"moles_reactants": 2,
"moles_products": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/le-chatelier-pressure-shift",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"moles_reactants": 2,
"moles_products": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/le-chatelier-pressure-shift", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"moles_reactants":2,"moles_products":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"moles_reactants":2,"moles_products":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/le-chatelier-pressure-shift", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"moles_reactants": 2,
"moles_products": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.le_chatelier_pressure_shift",
"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_moles | 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 Le Chatelier predicts when pressure increases
The response echoes moles_reactants and moles_products, reports delta_n_gas as products minus reactants, names the fewer_moles_side, and tags direction as reverse or forward with shift labels toward_reactants or toward_products. There is no Monte Carlo path and no temperature model: either the totals differ and a deterministic side is returned, or the totals match and the request fails with invalid_input.
How mole totals are read and when equal counts are rejected
Values may be numbers or decimal strings, including optional scientific notation when they parse as finite; non-numeric tokens, empty strings, and magnitudes above the documented ceiling are rejected with a clear message so a bad cell does not become a wrong shift. Zero on one side is valid—for example a reaction that produces gas from only condensed reactants—and simply means that side contributes no gas particles. The comparison itself is a pure numeric inequality: if reactant gas moles are smaller, pressure increase favors reactants; if product gas moles are smaller, it favors products. The preferred fields are moles_reactants for the sum of gaseous reactant coefficients and moles_products for the sum of gaseous product coefficients, but aliases such as n_reactants, gas_moles_reactants, reactants, and n_left for the left side, and n_products, gas_moles_products, products, and n_right for the right side are accepted so spreadsheets, query strings, and typed forms can reuse the same contract. Both totals must be non-negative: negative gas moles from stoichiometry are chemically meaningless and trigger invalid_input. When the two totals are equal within a tiny relative epsilon, the tool refuses the request rather than inventing a no-shift success payload, because homework and API clients often need an explicit error when pressure cannot select a side. Pair the free browser run on this page with the priced API when you need the identical classification inside an automated pipeline.
Where pressure-shift checks fit in study, lab, 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 Q-versus-K direction, Kp from partial pressures, or Gibbs-based K tools when you need related equilibrium steps, and with other chemistry endpoints when you are building a small lab of free, deterministic helpers.
Integration use cases
Deterministic test fixtures
Generate reproducible shift tags and delta_n_gas values for unit tests, tutoring software, and CI assertions on Le Chatelier pressure rules.