question about Gas Laws

日和月

2012-10-11 3:51 am

According to Boyle Law,PV=constant, Pressure Law ,P/T=constant and Charle Law,V/T = constant .
If T increase,P increase by Presure Law, then V will decrease by Boyle law.However,it seem to contradict to Charles law(V increase with T increase) Why?Please give detailed explanation.

回答 (1)

天同

2012-10-11 6:55 am

✔ 最佳答案

Each physical law must have some condition for it to be valid. The conditions for the three gas laws that you mentioned are:
For Boyle' Law to hold, the temperature of the gas must be kept constant;
For Charle's Law to hold, the gas must be under a constant pressure;
For Pressure Law to hold, the volume of the gas must be fixed.

Under the situation that the pressure, volume and temperature are free to vary, then the ideal gas equation holds, i.e. PV/T = constant, for a given mass of gas.

The "constant" actually depends on the mass of the gas and is given by n.R, where n is the no. of moles of the gas and R is the universal gas constant (= 8.31 J/mol.K).

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