Chemistry Calculators

#1 Free Molar Volume Calculator 2025

3 days ago
2 mins
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Molar Volume Calculator

Ideal Gas (Vm = RT/P)

Real Substance (Vm = Molar Mass / Density)

Calculation Result

Step-by-step Solution:

Molar volume (Vm) is the volume occupied by one mole of a substance (a chemical element or chemical compound) at a given temperature and pressure. It is a fundamental property in chemistry and physics, helping to understand the relationship between the macroscopic volume of a substance and the amount of matter it contains at the molecular level.

Ideal Gases: For an ideal gas, the molar volume can be calculated using the Ideal Gas Law (PV = nRT). At Standard Temperature and Pressure (STP: 0 °C and 1 atm), the molar volume of an ideal gas is approximately 22.414 L/mol. At Standard Ambient Temperature and Pressure (SATP: 25 °C and 1 bar), it's approximately 24.79 L/mol.

Real Substances (Solids, Liquids, Real Gases): For real substances, the molar volume is typically determined by its molar mass (M) and density (ρ). Unlike ideal gases, the molar volume of real substances depends significantly on the phase (solid, liquid, gas) and intermolecular forces.

The unit of molar volume is typically liters per mole (L/mol), cubic centimeters per mole (cm³/mol or mL/mol), or cubic meters per mole (m³/mol).

1. For Ideal Gases:

The molar volume (Vm) is derived from the Ideal Gas Law: PV = nRT

So, Vm = V/n = RT/P

  • Vm = Molar Volume
  • R = Ideal Gas Constant (8.31446 J/(mol·K) or Pa·m³/mol·K; or 0.082057 L·atm/(mol·K))
  • T = Absolute Temperature (in Kelvin, K)
  • P = Absolute Pressure (in Pascals, Pa, or atmospheres, atm)

This calculator internally converts temperature to Kelvin and pressure to Pascals for calculation with R = 8.31446 J/(mol·K) to get Vm in m³/mol, then converts to your desired output unit.

2. For Real Substances (from Molar Mass and Density):

Vm = M / ρ

  • Vm = Molar Volume
  • M = Molar Mass (typically in g/mol)
  • ρ = Density (typically in g/cm³ or kg/m³)

This calculator internally converts density to g/cm³ if molar mass is in g/mol, to get Vm in cm³/mol, then converts to your desired output unit.

1. Select Calculation Mode:

  • Choose "Ideal Gas" if you want to calculate molar volume based on temperature and pressure, assuming ideal gas behavior.
  • Choose "Real Substance" if you have the molar mass and density of a substance.

2. Enter Input Values:

  • For Ideal Gas:
    • Enter the temperature and select its unit (°C, K, or °F).
    • Enter the pressure and select its unit (atm, Pa, kPa, mmHg, or psi).
  • For Real Substance:
    • Enter the molar mass (typically in g/mol).
    • Enter the density and select its unit (g/cm³, kg/m³, or g/L).

3. Select Desired Output Unit:

  • Choose the unit in which you want the molar volume to be displayed (L/mol, cm³/mol, or m³/mol).

4. Calculate:

  • Click the "Calculate Molar Volume" button.

5. View Results:

  • The calculated molar volume will be displayed, along with a detailed step-by-step solution showing how the result was obtained.
  • If there are any errors in your input (e.g., non-numeric values, invalid conditions like zero pressure), an error message will appear.

6. Reset:

  • Click the "Reset" button to clear all input fields and results, allowing you to start a new calculation.

7. Explore Information:

  • Click on the "Theory," "Formulas," or "Instructions" bars to expand or collapse detailed information about molar volume and the calculator.
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