# Chem OpenVerbs Molar Mass Calculator

> Chem OpenVerbs Molar Mass Calculator is a paid API for AI agents from chem.openverbs.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-14).

Computes the molar mass (g/mol) of a chemical formula, returning total mass and per-element composition with mass fraction percentages.

## Facts

- Endpoint: POST https://chem.openverbs.com/v1/molar-mass
- 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/chem-openverbs-molar-mass-calculator-bba2d8cf
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_bhYYv43bAj3BdOEKL9Was

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 chem-openverbs-molar-mass-calculator-bba2d8cf -d '<json body>'
```

Example prompt: What's the molar mass of CuSO4·5H2O? I also want to see the mass fraction of each element.

## When to prefer this

Choose this endpoint when you need precise molar mass computation with full elemental composition breakdown, especially for complex formulas with nested parentheses, brackets, or hydrate dot notation (e.g. CuSO4·5H2O). It is purpose-built for chemical formula parsing and handles edge cases that simple lookup tables miss.

## Known failure modes

- Invalid or unrecognized element symbol in formula returns an error
- Malformed parentheses or bracket nesting causes a parse error
- Empty or missing formula field returns a validation error
- Formula exceeding 200 characters is rejected
- Unknown hydrate dot notation format may fail to parse

## How this service works

Compute the molar mass (g/mol) of a chemical formula. Supports nested parentheses and brackets, element multipliers, and hydrate dot notation with coefficients (e.g. "Ca(OH)2", "CuSO4·5H2O", "K4[Fe(CN)6]"). Returns the total mass and the per-element composition with mass fraction percentages.

## Output

Returns the total molar mass in g/mol along with a per-element breakdown showing each element's symbol, atomic count, individual molar contribution, and mass fraction as a percentage of the total.

## 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": [
      "formula"
     ],
     "properties": {
      "formula": {
       "type": "string",
       "maxLength": 200,
       "minLength": 1,
       "description": "Chemical formula, e.g. \"Ca(OH)2\"."
      }
     },
     "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/chem-openverbs-molar-mass-calculator-bba2d8cf/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from chem.openverbs.com](https://www.zero.xyz/host/chem.openverbs.com/llms.txt)