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Monday, July 8, 2019

IF Problems

Once we understand the five laws we can solve IF problems, also known as combined gas law problems.

I call them IF problems because they involve an INITIAL state and a FINAL state.

As an example, look at this problem:
A child is holding a 5.00 L helium-filled balloon. The temperature of the balloon is 294 K and the pressure inside the balloon is 0.966 atm. If the child accidentally lets go of the balloon and it floats up to a place high in the sky where the temperature is only 261 K and the pressure drops to 0.78 atm, what will be the new volume of the balloon? 


It is worth noting that temperatures are rarely recorded in Kelvin, but we'll deal with in the next problem. There are two ways to solve these problems. One is purely algebraic, requiring no knowledge of gas laws at all. That process is shown here. The second way to solve an IF problem is to imagine each variable changing separately. This process requires (and therefore reinforces) an understanding of the gas laws, but not much algebra.

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