# ChemEq Stoichiometry Calculator

> ChemEq Stoichiometry 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 a known amount of one species, computes the amount of a target species using auto-balanced stoichiometry.

## Facts

- Endpoint: POST https://chemeq.openverbs.com/v1/stoichiometry
- 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-stoichiometry-calculator-76cf2615
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_-_4lJ4xtbpM9k0p4qIM2l

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-stoichiometry-calculator-76cf2615 -d '<json body>'
```

Example prompt: For the reaction H2 + O2 -> H2O, if I start with 5 moles of H2, how many grams of water will be produced?

## When to prefer this

Use this endpoint when you need to determine how much of a product or reactant is involved in a chemical reaction given a known quantity of another species, and you want automatic equation balancing included. Prefer this over manual stoichiometry when the equation may be unbalanced or when converting between mass and mole units across species.

## Known failure modes

- Invalid or unparseable chemical equation returns an error
- Species specified in 'given' or 'target' not found in the equation
- Unrecognized element symbols cause parsing failure
- Zero or negative amount values may produce errors or nonsensical output
- Missing required fields (equation, given species/amount, target) return validation errors

## How this service works

Given a reaction and a known amount (moles or grams) of one species, compute the amount of a target species. The equation is balanced automatically.

## Output

A numeric amount of the target species expressed in the requested unit (mol or g), computed using the stoichiometric ratios derived from the auto-balanced reaction equation.

## 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",
      "given",
      "target"
     ],
     "properties": {
      "given": {
       "type": "object",
       "required": [
        "species",
        "amount"
       ],
       "properties": {
        "unit": {
         "enum": [
          "mol",
          "g"
         ],
         "type": "string",
         "description": "Unit of `amount`. Default \"mol\"."
        },
        "amount": {
         "type": "number",
         "description": "Known amount of the given species."
        },
        "species": {
         "type": "string",
         "minLength": 1,
         "description": "A species appearing in the equation."
        }
       },
       "additionalProperties": false
      },
      "target": {
       "type": "string",
       "minLength": 1,
       "description": "The species to solve for."
      },
      "equation": {
       "type": "string",
       "minLength": 1,
       "description": "Reaction, e.g. \"H2 + O2 -> H2O\"."
      },
      "targetUnit": {
       "enum": [
        "mol",
        "g"
       ],
       "type": "string",
       "description": "Unit for the target result. Default \"mol\"."
      }
     },
     "additionalProperties": false
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

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