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Combined Gas Law (final pressure)

vCalc Reviewed
`P_(f) = ( T_f * P_i * V_i ) / ( T_i * V_f ) `
`(V_i)"Initial Volume"`
`(V_f)"Final Volume"`
`(T_i)"Initial Temperature"`
`(T_f)"Final Temperature"`
`(P_i)"Initial Pressure"`
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The Combined Gas Law (Final Pressure) computes the final pressure based on the initial and final temperatures and volumes and the initial pressure.

INSTRUCTIONS: Choose units and enter the following:

  • (Pi) Initial Pressure
  • (Ti) Initial Temperature
  • (Tf) Final Temperature
  • (Vi) Initial Volume
  • (Vf) Final Volume

Final Pressure (Pf): The calculator return the final pressure in pascals. However, this can be automatically converted to compatible units via the pull-down menu.

The Math / Science

The Combined Gas Law  associates the pressure, volume, temperature and a constant of a gas, based on a combination of Charles's law, Boyle's law, and Gay-Lussac's law. There is no 'official' founder for this law because it is a consolidation of the three other laws.  The combined gas law states the ratio between the pressure-volume product and the temperature of a system remains constant (k).  This constancy can be used when comparing different conditions using the same substances. The combined gas law is mathematically expressed as follows:

`(P_i V_i)/(T_i) = (P_(f) V_f)/(T_f) = k`

The Combined Gas Law calculator groups the forms of the Combined Gas Law formula in two ways as follows:

P • V / T = k 

  • Pressure based on known volume, temperature and the combined gas constant.
  • Volume based on know pressure, temperature and the combined gas constant.
  • Temperature based on known pressure, volume and the combined gas constant.
  • k gas constant based on the proportionality of the gas if you know pressure, volume and the temperature for the specific gas.

Pi • Vi/Ti = Pf • Vf/Tf

Since P•V/T = k, one can compute the initial (i) and final (f) states using the expanded version of the Combined Gas Law. The Pi • Vi/Ti = Pf • Vf/Tf tab allows the user to enter any five of the six values in the formula to compute the remaining one via the Combined Gas Law.

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