Honestly, I've never used P1V1/n1T1 = P2V2/n2V2.
I think PV = nRT will solve all of them. If all except one variable are given out of P1, P2, V1, V2, T1 and T2, then I use P1V1/T1 = P2V2/T2 (because it's a little faster) but I could use PV = nRT twice; once to solve P1V1/R*T1 for n, then use PV = nRT again with that n and P2, V2, for example, and solve for T2. So I don't know that it matters which you use. Check my thinking.
I know how to use the equations pv=nrt and P1xV1/n1xT1 = P2xV2/n2xT2, but I don't understand when to use them.
I have a test tomorrow and I'm going over some word problems, but I can't figure out how decide which formula you need to use. Is there a specific way to know?
4 answers
I was thinking that if, for example, two different pressures were given, two different volumes were given, two different temperatures were given and only one mole, then you use P1V1/n1T1...etc to find the missing mole.
But, if only one pressure, one volume, and one temperature were given and you needed to find moles, then you use pv=nrt.
That's how I tried figuring out the difference, but I was afraid there was some exception to throw me off (which usually always happens on tests...)
But, if only one pressure, one volume, and one temperature were given and you needed to find moles, then you use pv=nrt.
That's how I tried figuring out the difference, but I was afraid there was some exception to throw me off (which usually always happens on tests...)
I think your thinking is OK. I tried making up a P1, V1, T1 and calculating n1. Then I made up a P2, V2, T2 and calculated n2, both calculations from PV = nRT.
Then I used the old P1, V1, T1, and the calculated n1 and the old P2, V2, and calculated n2 and calculated T2 from the P1V1/n1T1 = P2V2/n2T2 equation and got the same answer. In fact I tried it with two or three sets of numbers and I always came out with the same answer no matter which way I solved it. Of course, if only ONE P, V, and T are given, you have no choice but to use PV = nRT.
Then I used the old P1, V1, T1, and the calculated n1 and the old P2, V2, and calculated n2 and calculated T2 from the P1V1/n1T1 = P2V2/n2T2 equation and got the same answer. In fact I tried it with two or three sets of numbers and I always came out with the same answer no matter which way I solved it. Of course, if only ONE P, V, and T are given, you have no choice but to use PV = nRT.
Okay, good. I think I'm all set then. Thank you!
1 answer