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Sealed-Volume Gas Pressure, Temperature and Amount

Relate two positive ideal-gas states with fixed volume and amount, preserve editable units and inverse controls, and calculate optional amount through the initial state.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Formula and method

At fixed volume and amount, heating from 300 to 600 K changes absolute pressure from 100,000 to 200,000 Pa.

p₁/T₁ = p₂/T₂; p₁V = nRT₁

Worked example

Enter these known values and leave the other values blank.

Initial pressure (p₁)
100000 Pa
Initial temperature (T₁)
300 K
Final temperature (T₂)
600 K
Final pressure (p₂)
200000 Pa

Assumptions and limitations

  • Hold volume and amount constant between the two states. This finite ideal-gas workflow requires positive absolute pressure, volume, Kelvin temperature and amount; it excludes zero and negative absolute states.
  • Temperature entries in Celsius or Fahrenheit are converted to absolute Kelvin before ratios or pV=nRT. Negative Celsius can be valid above −273.15°C. Pressure must be absolute, not an unadjusted gauge reading.
  • Supply three independent two-state measures to recover the fourth. The extra initial-state pV=nRT relation supports its missing pressure, volume, temperature or molar amount from the other three; the universal molar constant is distinct from a substance-specific constant per kilogram. Clear a desired unknown before solving backward.
  • The model assumes a fixed amount of ideal gas without leakage or phase change. It does not model condensation, high-density interactions, reaction or changing amount. The retained gas constant is modernized to the exact SI value.
  • The pressure unit inHg uses conventional mercury at 0°C and standard gravity, with 1 inHg = 3386.388640341 Pa; mmHg uses the corresponding 133.322387415 Pa factor. Torr is 101325/760 Pa, which is close but not identical to that mmHg convention.

Common questions

What must stay fixed in this two-state law?

Keep volume and amount fixed. Use absolute temperature and absolute pressure. A different path or a changing gas amount requires a different relation.

Can I use Celsius or Fahrenheit?

Yes. The selected temperature unit is converted to Kelvin before calculation. For example, 0°C means 273.15 K; temperature ratios do not use the displayed Celsius values directly.

What do the additional amount controls do?

They retain the initial-state ideal-gas relationship pV=nRT. Enter its three known quantities to recover the fourth. Amount here means moles, not mass in kilograms.

References

Use the exact SI molar gas constant R = N_A k_B = 8.31446261815324 J/(mol·K), replacing the captured 8.3144598 in the ideal-gas equation and every inverse; the two-state ratio law is unchanged. Mercury pressure columns use conventional density and standard gravity, with the exact international inch. Pounds-force per square inch use the exact international pound and inch with standard gravity, replacing the rounded captured factor. One technical atmosphere is exactly one kilogram-force per square centimeter under standard gravity.

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