Molar solubility from Ksp calculator
A 1:1 salt with a Ksp of 1.8 × 10⁻¹⁰ dissolves to 0.000013416408 mol/L. Enter the Ksp and the number of cations and anions per formula unit to get the molar solubility and each ion's concentration at saturation. Free in your browser.
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- Your data stays on your device
Run — free
Worked example
- Solubility product constant Ksp
- 0.0000000002
- Cation coeff
- 1
- Anion coeff
- 1
- Molar solubility
- 0.0000134164
- Cation concentration
- 0.0000134164
- Anion concentration
- 0.0000134164
- Dissociation
- MA(s) ⇌ 1 M + 1 A
Molar solubility is the equilibrium amount of a sparingly soluble salt that dissolves per liter of saturated solution, expressed in moles per liter. From the solubility product Ksp and the dissociation stoichiometry of MxAy into x cations and y anions, the relation Ksp equals x to the x times y to the y times s to the x plus y yields a unique non-negative s that students, lab notebooks, and process scripts can compute without re-deriving the algebra each time.
What molar solubility from Ksp returns and how to choose Ksp and stoichiometry
Write the dissolution equilibrium as solid MxAy producing x moles of cation M and y moles of anion A per formula unit that dissolves. At saturation, ion concentrations are [M] equals x times s and [A] equals y times s, so the solubility product is Ksp equals open parenthesis x s close parenthesis to the x times open parenthesis y s close parenthesis to the y, which factors as x to the x times y to the y times s to the x plus y.
Solving for s gives s equals the quantity Ksp divided by x to the x times y to the y, all raised to the power one over x plus y. Common classroom patterns include AB salts with x equals one and y equals one so s is the square root of Ksp; AB2 salts with x equals one and y equals two so s is the cube root of Ksp over four; and A2B3-type patterns with larger integers.
Negative Ksp is invalid input because a negative solubility product is unphysical for this contract and would hide bad data instead of failing loudly. Zero Ksp is accepted and yields zero molar solubility. Coefficients must be positive integers in the published range so the power expressions stay classroom-safe.
What you can do with it
Homework and lab report checks
Students compute molar solubility from textbook Ksp and MxAy stoichiometry, compare s and ion concentrations against hand work, and get a clear error when a negative Ksp is entered by mistake.
Water quality and sparingly soluble salts
Monitoring tools convert a tabulated Ksp and known salt stoichiometry into saturated molar solubility for hardness, scaling, or precipitate estimates.
Process and formulation screening
Lightweight process scripts estimate how much of a sparingly soluble salt dissolves at equilibrium from Ksp and formula-unit coefficients without embedding a full speciation library.
FAQ
What happens if Ksp is negative?
A negative solubility product is rejected as unphysical for this calculator and is not charged after validation fails.
Is the molar solubility from Ksp calculator free?
The browser tool runs free on your device.
Does this include the common-ion effect?
Supply an effective Ksp or a different model if common ions or activities matter.
What is the molar solubility of a 1:1 salt with a Ksp of 1.8 × 10⁻¹⁰?
It is 0.000013416408 mol/L, the square root of the Ksp. With one cation and one anion per formula unit, both ions end up at that same concentration in the saturated solution.
How does the calculation change for a salt like AB2?
With one cation and two anions, the molar solubility is the cube root of the Ksp divided by four. In general, the Ksp is divided by x to the x times y to the y and raised to one over x plus y.
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/molar-solubility-from-ksp \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"ksp":1.8e-10,"cation_coeff":1,"anion_coeff":1}'const res = await fetch("https://api.kit.forhosting.com/chem/molar-solubility-from-ksp", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"ksp": 1.8e-10,
"cation_coeff": 1,
"anion_coeff": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/molar-solubility-from-ksp",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"ksp": 1.8e-10,
"cation_coeff": 1,
"anion_coeff": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/molar-solubility-from-ksp", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"ksp":1.8e-10,"cation_coeff":1,"anion_coeff":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"ksp":1.8e-10,"cation_coeff":1,"anion_coeff":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/molar-solubility-from-ksp", 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_coeff": 1,
"anion_coeff": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.molar_solubility_from_ksp",
"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 closed form deterministically, returns equilibrium ion concentrations as x s and y s, rejects a negative Ksp with a clear invalid input error, and emits structured JSON that homework checkers, water-chemistry tools, and lightweight pipelines can pin in tests.
What molar solubility from Ksp returns and how to choose Ksp and stoichiometry
Send required fields ksp, cation_coeff, and anion_coeff as JSON numbers or numeric strings; aliases Ksp, K_sp, and solubility_product map to ksp, while x, cation, cations, and m map to the cation coefficient and y, anion, anions, and n map to the anion coefficient. Identical inputs always produce identical JSON because the path is pure arithmetic with no network, no random seed, and no wall clock.
Reading molar solubility, ion concentrations, formula labels, and units
On success the response echoes ksp, cation_coeff, and anion_coeff, reports molar_solubility as s, and reports cation_concentration and anion_concentration as x s and y s so grading software can check ions separately from the salt solubility. The formula field always restates s equals open parenthesis Ksp over x to the x times y to the y close parenthesis to the one over x plus y, dissociation labels the MxAy equilibrium in compact text, and method is always molar_solubility_from_ksp so downstream code can branch without sniffing shapes. A units_note field reminds integrators that s and the ion concentrations are in moles per liter when Ksp is written with consistent molar concentration units raised to x plus y. Use molar_solubility alone when a pipeline only needs how much salt dissolves; use the ion concentrations when a precipitation or common-ion follow-on step needs [M] and [A]; use formula and dissociation when UIs display the equation next to the number. Missing fields, non-finite numbers, non-integer or out-of-range coefficients, and negative Ksp 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 molar solubility from Ksp calculator for homework checks, lecture demos, and quick saturated-solution estimates without installing a full aqueous-chemistry package. Common-ion effects, activity coefficients, complexation, and temperature dependence of Ksp are outside this calculator: supply an effective Ksp already corrected for your conditions if the application demands it. Send a JSON body with required ksp, 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 equilibrium-constant helpers when you first obtain Ksp from tabulated data or from measured ion concentrations, then feed Ksp and stoichiometry here to recover s. Authors shipping SDKs can map molar_solubility and the ion concentrations directly into dashboards that show how much solid dissolves next to the Ksp and formula unit used.
Technical questions
How do I compute molar solubility from Ksp?
Send JSON with ksp, cation_coeff (x), and anion_coeff (y) for MxAy. The response molar_solubility is s = (Ksp / (x^x · y^y))^(1/(x+y)), with ion concentrations x s and y s.
What stoichiometry should I use for AB2 salts?
Use cation_coeff 1 and anion_coeff 2 (or the reverse if your convention swaps labels). Then Ksp = 4 s^3 and s is the cube root of Ksp over four.