Precipitation ion product calculator
With a Ksp of 1.8 × 10⁻¹⁰ and both ions at 0.0001 mol/L in a one-to-one salt, Q is 10⁻⁸, so a precipitate forms. Enter the post-mix concentrations, the coefficients and Ksp to see whether a solid will appear. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Solubility product constant Ksp
- 0.0000000002
- Cation concentration
- 0.0001
- Anion concentration
- 0.0001
- Cation coeff
- 1
- Anion coeff
- 1
- Ion product
- 0.00000001
- Q over ksp
- 55.5555555556
- Comparison
- Q > Ksp
- Status
- precipitate
Whether a solid forms when two ionic solutions are mixed is decided by comparing the ion product Q to the solubility product Ksp of the sparingly soluble salt that might precipitate. With post-mix molar concentrations of the cation and anion and the stoichiometric coefficients of MxAy, Q equals the cation concentration to the power x times the anion concentration to the power y; if Q exceeds Ksp the solution is supersaturated and a precipitate is expected, if Q is less than Ksp no precipitate forms, and if they match the system sits at saturated equilibrium.
What the ion product test returns and how to prepare concentrations
Write the potential precipitation equilibrium as solid MxAy producing x moles of cation M and y moles of anion A per formula unit. After you mix reagents and account for dilution, you hold the instantaneous molar concentrations of the free cation and free anion that enter the ion product. The reaction quotient for dissolution is Q equals open parenthesis M close parenthesis to the x times open parenthesis A close parenthesis to the y, using the same concentration basis as tabulated Ksp, almost always moles per liter.
Classic classroom patterns include one-to-one salts such as silver chloride where Q is simply the product of the two concentrations, and one-to-two salts such as calcium fluoride where the fluoride concentration is squared. Coefficients x and y must be positive integers in the published classroom range. Negative concentrations are invalid input because a negative molarity is unphysical for this product and would hide bad data instead of failing loudly.
Zero concentrations are accepted and typically yield Q equal to zero, so no precipitate when Ksp is positive.
What you can do with it
Homework and exam precipitation checks
Students compute Q from post-mix ion concentrations and stoichiometry, compare Q to textbook Ksp, and get a clear error when a negative concentration is entered by mistake.
Water quality and scaling screens
Monitoring tools combine measured hardness ions with a tabulated Ksp to flag whether a sparingly soluble salt is expected to precipitate under current conditions.
Process and formulation mix tests
Lightweight process scripts decide if mixing two reagent streams will form a solid from Q versus Ksp without embedding a full multi-equilibrium solver.
FAQ
What happens if a concentration is negative?
Negative molar concentrations are unphysical for this calculator and are rejected without charge after validation.
Is the precipitation ion product calculator free?
The browser tool runs free on your device.
How do I know if a precipitate will form?
Compute the ion product Q from the concentrations after mixing and compare it with Ksp. If Q is greater, a precipitate is expected; if it is smaller, nothing precipitates; if they are equal, the solution is saturated.
Should I use the concentrations before or after mixing?
After mixing. When two solutions are combined, each ion is diluted by the extra volume, and it is that diluted concentration that goes into Q, in the same units as the Ksp you are using.
Why is the fluoride concentration squared for calcium fluoride?
Because each formula unit releases two fluoride ions, so the anion coefficient is 2 and becomes the exponent in Q. For a one-to-one salt such as silver chloride, Q is simply the two concentrations multiplied.
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/will-precipitate \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"ksp":1.8e-10,"cation_concentration":0.0001,"anion_concentration":0.0001,"cation_coeff":1,"anion_coeff":1}'const res = await fetch("https://api.kit.forhosting.com/chem/will-precipitate", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"ksp": 1.8e-10,
"cation_concentration": 0.0001,
"anion_concentration": 0.0001,
"cation_coeff": 1,
"anion_coeff": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/will-precipitate",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"ksp": 1.8e-10,
"cation_concentration": 0.0001,
"anion_concentration": 0.0001,
"cation_coeff": 1,
"anion_coeff": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/will-precipitate", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"ksp":1.8e-10,"cation_concentration":0.0001,"anion_concentration":0.0001,"cation_coeff":1,"anion_coeff":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"ksp":1.8e-10,"cation_concentration":0.0001,"anion_concentration":0.0001,"cation_coeff":1,"anion_coeff":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/will-precipitate", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"ksp": 1.8e-10,
"cation_concentration": 0.0001,
"anion_concentration": 0.0001,
"cation_coeff": 1,
"anion_coeff": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.will_precipitate",
"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.
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
This capability evaluates that test deterministically, returns structured fields for Q, the Q over Ksp ratio, a boolean will_precipitate flag, and a human-readable comparison string, rejects negative ion concentrations with a clear invalid input error, and emits JSON that homework checkers, lab notebooks, and water-chemistry pipelines can pin in tests.
What the ion product test returns and how to prepare concentrations
Send required fields ksp, cation_concentration, anion_concentration, cation_coeff, and anion_coeff as JSON numbers or numeric strings; aliases Ksp, K_sp, and solubility_product map to ksp, while cation_conc, cation, and related keys map to the cation concentration and anion_conc, anion, and related keys map to the anion concentration. Identical inputs always produce identical JSON because the path is pure arithmetic with no network, no random seed, and no wall clock.
Reading ion product, Q over Ksp, will_precipitate, and status labels
On success the response echoes ksp, both ion concentrations, and both stoichiometric coefficients, then reports ion_product as Q and q_over_ksp as the ratio of Q to Ksp when that ratio is finite. The boolean will_precipitate is true only when Q is strictly greater than Ksp under a tiny relative tolerance that keeps floating-point noise from flipping the edge; when Q and Ksp match within tolerance the comparison string is Q equals Ksp and status is equilibrium with will_precipitate false; when Q is below Ksp the status is no_precipitate. The formula field always restates Q equals cation to the x times anion to the y with the rule precipitate if Q greater than Ksp, dissociation labels the MxAy equilibrium in compact text, and method is always will_precipitate so downstream code can branch without sniffing shapes. A units_note reminds integrators that concentrations and Ksp must share a consistent unit system. Use will_precipitate alone for a yes-or-no gate in a lab script; use ion_product and comparison when a report must show the intermediate Q value next to Ksp; use status when a UI needs three-way wording for supersaturated, unsaturated, and saturated. Missing fields, non-finite numbers, out-of-range coefficients, negative Ksp, and negative concentrations all fail with invalid_input and are not charged after the engine rejects the request.
API usage, pricing, lab workflows, and practical limits
Call the free in-browser precipitation ion product calculator for homework checks, lecture demos, and quick mix-and-predict estimates without installing a full aqueous speciation package. Common-ion effects, activity coefficients, complexation, nucleation kinetics, and temperature dependence of Ksp are outside this calculator: supply concentrations and an effective Ksp already corrected for your conditions if the application demands it. Send a JSON body with required ksp, cation_concentration, anion_concentration, cation_coeff, and anion_coeff. Use the prepaid API when an environmental monitoring stack, water-treatment tool, pharmaceutical salt-screening script, or chemistry homework platform needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after rejection. Pair this endpoint with a molar-solubility-from-Ksp helper when you first need the saturated concentrations of a pure salt, then feed measured or planned post-mix concentrations here to decide whether adding another ion source will force precipitation. Authors shipping SDKs can map will_precipitate, ion_product, and comparison directly into dashboards that show whether a mixture is expected to drop a solid next to the Q and Ksp numbers used.
Technical questions
How do I predict whether a precipitate forms?
Send JSON with ksp, cation_concentration, anion_concentration, cation_coeff (x), and anion_coeff (y). The response includes ion_product Q, comparison of Q to Ksp, and will_precipitate true only when Q > Ksp.
What is the ion product Q?
For MxAy(s) ⇌ x M + y A, Q = [M]^x [A]^y using the same concentration units as Ksp. It is the reaction quotient evaluated at the current ion concentrations before equilibrium is re-established.
Does Q equal to Ksp count as a precipitate?
No. When Q matches Ksp within a tiny relative tolerance, status is equilibrium and will_precipitate is false—the system is saturated with no driving force for net precipitation.