CALCULATORS / PROCESS AND CHEMICAL ENGINEERING ESTIMATES

Gas-mixture composition and density calculator

Ideal binary gas mole-fraction molar mass and partial pressure.

chemistry-gas-mixture.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	molarMassg/mol	partialAkPa
	28.8	80
	29.44	64

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

mole fraction bound0.80 ✓ passes

BASELINE INPUTS

fractionA0.8 molarMassA28 g/molmolarMassB32 g/molpressure100 kPa

CALCULATED

molarMass28.8 g/mol

partialA80 kPa

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Gas-mixture composition and density
# Scope: Ideal binary gas mole-fraction molar mass and partial pressure.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

fractionA = 0.8
molarMassA = 28 g/mol
molarMassB = 32 g/mol
pressure = 100 kPa

molarMass := fractionA*molarMassA+(1-fractionA)*molarMassB [g/mol]
partialA := fractionA*pressure [kPa]

check mole fraction bound: fractionA <= 1

scenario alternative: fractionA = 0.64

Calculated from your source · not saved

Baseline · Baseline

mole fraction bound0.80 ✓ passes

alternative · alternative

mole fraction bound0.64 ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

molar mass: molarMass = fractionA*molarMassA+(1-fractionA)*molarMassB [g/mol]
partial a: partialA = fractionA*pressure [kPa]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

fraction a: 0.8
molar mass a: 28 g/mol
molar mass b: 32 g/mol
pressure: 100 kPa

Calculated

molar mass: 28.8 g/mol
partial a: 80 kPa

Assumptions and limits

Ideal binary gas mole-fraction molar mass and partial pressure.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Gas-mixture composition and density. Inputs: composition; molecular masses; pressure; temperature. Outputs: molecular weight; ideal density; partial pressures. Model scope: Specified chemistry and low-order mass/energy balances. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: composition, molecular masses, pressure, temperature
Outputs: molecular weight, ideal density, partial pressures
Modes: calculate, compare, sweep
Drawing: Process balance diagram

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS