# ChemEq Limiting Reagent Calculator

> ChemEq Limiting Reagent Calculator is a paid API for AI agents from chemeq.openverbs.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-14).

Given a chemical reaction equation and supplied amounts of all reactants, identifies the limiting reagent and computes leftover amounts of excess reactants plus theoretical product yields.

## Facts

- Endpoint: POST https://chemeq.openverbs.com/v1/limiting
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/chemeq-limiting-reagent-calculator-5c6b056f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_xgwYEOqSIwEjzjpmEEsHQ

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability chemeq-limiting-reagent-calculator-5c6b056f -d '<json body>'
```

Example prompt: I have 5 mol of N2 and 12 mol of H2 reacting in N2 + 3H2 -> 2NH3 — which is the limiting reagent, how much excess reactant is left over, and what's the theoretical yield of NH3?

## When to prefer this

Choose this endpoint when you need to determine which reactant is limiting in a given chemical reaction and want quantitative results for leftover reactants and theoretical product yields. Prefer this over a general stoichiometry endpoint when the specific task is limiting-reagent identification given full reactant quantities. Use the sibling stoichiometry endpoint instead if you only know the amount of one species and want to find amounts of another.

## Known failure modes

- Unbalanceable or invalid equation string causes a parse error
- Amounts array missing a required reactant species returns a validation error
- Non-positive or zero amounts may cause computation errors
- Specifying an unknown or misspelled chemical species returns an error
- Providing amounts in inconsistent units without specifying unit field may default to mol unexpectedly

## How this service works

Given a reaction and the supplied amount of every reactant, identify the limiting reagent and compute leftover reactant and theoretical product yields.

## Output

Returns the identified limiting reagent, the remaining (leftover) amount of each excess reactant after the reaction is complete, and the theoretical maximum yield of each product species, typically expressed in moles or grams consistent with the input units.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "equation",
      "amounts"
     ],
     "properties": {
      "amounts": {
       "type": "array",
       "items": {
        "type": "object",
        "required": [
         "species",
         "amount"
        ],
        "properties": {
         "unit": {
          "enum": [
           "mol",
           "g"
          ],
          "type": "string",
          "description": "Default \"mol\"."
         },
         "amount": {
          "type": "number"
         },
         "species": {
          "type": "string",
          "minLength": 1
         }
        },
        "additionalProperties": false
       },
       "minItems": 1,
       "description": "Supplied amount of every reactant."
      },
      "equation": {
       "type": "string",
       "minLength": 1,
       "description": "Reaction, e.g. \"N2 + H2 -> NH3\"."
      }
     },
     "additionalProperties": false
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/chemeq-limiting-reagent-calculator-5c6b056f/health.json
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