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Why bother with a post grad? Are they even worth it? Have your say! 26-10-2016
1. How is the ideal gas equation a thing when each individual equation that's combined has it's own rules.

For example: Pressure is inversely proportional to volume at constant temperature. Then pressure is directly proportional to temperature when volume is constant.

How can you combine these things when the conditions aren't the same for each equation?

The Pressure law states that volume is constant and Boyles law states that temperature is constant. There are different conditions because volume isn't constant for Boyles law. I don't get how you can combine them if they aren't true for each others conditions. Can anyone help?
2. (Original post by Squishy•)
How is the ideal gas equation a thing when each individual equation that's combined has it's own rules.

For example: Pressure is inversely proportional to volume at constant temperature. Then pressure is directly proportional to temperature when volume is constant.

How can you combine these things when the conditions aren't the same for each equation?

The Pressure law states that volume is constant and Boyles law states that temperature is constant. There are different conditions because volume isn't constant for Boyles law. I don't get how you can combine them if they aren't true for each others conditions. Can anyone help?
First of all, I am assuming that you are referring to the combined gas law PV/T = constant.

As you already know, V/T = constant. This means that Vx/T1 = V2/T2

(where x is just a symbol indicating that Vx is different than V2 or V1)

PV = constant, so P1V1 = P2Vx

Solve for Vx in these two equations :

Equation 1: Vx = V2T1/T2

Substitute Vx in equation 2:

P1V1 = P2 * V2T1/T2

This gives us the combined gas law P1V1/T1 = P2V2/T2

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