Boiling point elevation calculator
See how far a dissolved solute pushes up the boiling point: 0.5 mol/kg with a water-like Kb of 0.512 adds 0.256 K, or 0.512 K when each formula unit splits into two particles. Enter molality, Kb and the van 't Hoff factor. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Molality
- 0.5
- Kb
- 0.512
- Current (A)
- 1
- Delta tb
- 0.256 K
- Precision
- 10
This boiling point elevation calculator returns the colligative temperature rise ΔTb of a dilute solution from molality m, the solvent ebullioscopic constant Kb, and the van 't Hoff factor i using the closed form ΔTb equals i times Kb times m. Boiling-point elevation is the increase of the boiling temperature of a solution relative to the pure solvent when a non-volatile solute lowers solvent vapor pressure. The same identity appears in general chemistry labs, osmotic and colligative problem sets, and process checks where you already know molality and need a reproducible kelvin (or Celsius-step) rise without table lookups. Typical textbook checks include water-like Kb about 0.512 K·kg/mol with m equals 0.5 mol/kg and i equals 1 yielding ΔTb equals 0.256 K, and the same m and Kb with i equals 2 for a strong 1:1 electrolyte yielding 0.512 K. The engine uses only finite arithmetic with no network calls, no sampling, and no date-dependent shortcuts.
What the boiling point rise tells you
Boiling-point elevation is a colligative property: for an ideal dilute solution of a non-volatile solute, the boiling temperature of the solution sits above that of the pure solvent by an amount proportional to the number of solute particles per kilogram of solvent.
The standard linear relation is ΔTb equals i times Kb times m, where m is molality in moles of solute per kilogram of solvent, Kb is the solvent-specific ebullioscopic constant with units K·kg/mol (numerically equal to °C·kg/mol for a temperature difference), and i is the van 't Hoff factor that counts the effective particles produced per formula unit. Ideal non-electrolytes use i equals one; strong electrolytes approach the stoichiometric ion count in the dilute limit, while weak electrolytes use an effective i between one and that count.
Zero molality is allowed and yields zero elevation.
Where boiling-point elevation fits in study, lab, and software
Students meet boiling-point elevation when a textbook introduces colligative properties after molality, when a lab report asks for the expected ΔTb of a prepared solution, or when a contest problem gives Kb and asks for the boiling temperature of a mixture relative to the pure solvent. Teachers can pre-generate answer keys for modest molalities and integer van 't Hoff factors without trusting opaque calculator apps that silently switch units or drop the particle factor.
Developers call the same contract from scripts to seed deterministic test vectors for chemistry education products, to normalize user-entered colligative inputs before plotting vapor-pressure curves, or to satisfy programming-challenge statements that demand ΔTb rather than a hand-waved estimate. Process and quality workflows sometimes need a fast offline source of elevation values so dilute-solution checks can be validated without reopening a full thermodynamics package.
Product and tutoring tools use the product when a learner types molality, Kb, and i and the UI must show a clean kelvin rise with a formula echo.
What you can do with it
Homework and lab ΔTb checks
Compute expected boiling-point rise from molality, solvent Kb, and van 't Hoff factor before writing lab reports or checking textbook answers.
Tutoring and chemistry software
Normalize user-entered m, Kb, and i into a stable kelvin elevation for interactive lessons and solution calculators.
FAQ
What does the boiling point elevation calculator cost?
It is free in your browser on this page.
What formula does this tool use?
ΔTb = i · Kb · m, where m is molality (mol/kg), Kb is the ebullioscopic constant (K·kg/mol), and i is the van 't Hoff factor.
What happens if molality is negative?
Molality cannot be negative for this colligative definition of boiling-point elevation.
Is the result in kelvin or degrees Celsius?
The elevation is returned in kelvin (unit K). For a temperature difference the numeric step matches °C, so 0.256 K is the same rise as 0.256 °C.
Does this tool look up Kb for common solvents?
No. You supply Kb (and i) for your solvent and solute. The calculator only multiplies the three inputs and returns ΔTb.
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/boiling-point-elevation \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"molality":0.5,"kb":0.512,"i":1}'const res = await fetch("https://api.kit.forhosting.com/chem/boiling-point-elevation", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"molality": 0.5,
"kb": 0.512,
"i": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/boiling-point-elevation",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"molality": 0.5,
"kb": 0.512,
"i": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/boiling-point-elevation", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"molality":0.5,"kb":0.512,"i":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"molality":0.5,"kb":0.512,"i":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/boiling-point-elevation", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"molality": 0.5,
"kb": 0.512,
"i": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.boiling_point_elevation",
"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 boiling-point elevation means and what the response contains
This calculator returns the normalized molality, kb, and i values, the elevation delta_tb rounded to the requested precision, the precision used, the method tag boiling_point_elevation, a short formula reminder, and the unit string K. There is no approximate CAS path and no random sampling: the engine either multiplies three finite scalars inside the supported magnitude range or rejects the input with invalid_input. Rejected cases include missing molality, kb, or i, non-finite values, magnitudes above the documented ceiling, and any negative molality, because a negative moles-per-kilogram figure is non-physical for this definition.
How molality, Kb, and the van 't Hoff factor are read
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 temperature rise. Zero molality is valid and simply returns a zero elevation. The constant and the factor are required finite numbers; you supply the solvent Kb and the particle factor that match your problem statement rather than relying on a hidden table. The preferred fields are molality for m, kb for the ebullioscopic constant, and i for the van 't Hoff factor, but aliases m, b, and molal for molality, Kb, ebullioscopic_constant, boiling_constant, and K_b for the constant, and van_t_hoff, vant_hoff, van_hoff, and factor for i are accepted so spreadsheets, query strings, and typed forms can reuse the same contract. Molality must not be negative: if the value is below zero, the request fails with invalid_input because colligative molality cannot be negative. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for molality, kb, i, and delta_tb, 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 ΔTb equals i Kb m yourself.
Where boiling-point elevation fits 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 molar-concentration or dilution tools when you need related solution chemistry steps, and with other chem endpoints when you are building a small lab of free, deterministic colligative helpers.
Integration use cases
Deterministic test fixtures
Generate reproducible delta_tb values for unit tests, property checks, and CI assertions on colligative formulas.