[candysell]

1.  We want to increase the volume of a fixed amount of gas from 57.3 to 165 mL while holding the pressure constant. To what value must we change the temperature if the initial temperature is 22 degree Celsius?
Right Answer: (576 degrees C)

For this one I used the equation I did for this chapter on gases.  Charles's Law V1/T1=V2/T2. It doesn't seem to work to get the answer.

2.  A 35.8-L cylinder of Ar(g) is connected to an evacuated 1875-L tank. If the temperature is held constant and the final pressure is 721 mmHg, what must have been the original gas pressure in the cylinder, in atmospheres?
Right Answer: (50.6 atm)

For this one I used Boyle's Law (P1)(V1)=(P2)(V2). It's also wrong.


I don't know how to solve these.  Please help.

[Corribus]

Didn't look at the second one, but the pitfall in the first one is the temperature unit.

[Corribus]

For the second one, show your calculation. My guess is you are doing something wrong with your volumes because you're not reading the problem carefully enough.  (Units may also be an issue here, so be careful with those.)

[candysell]

2. Just found this one out.  I forgot to convert mmHg to Atm. 

[candysell]

Didn't look at the second one, but the pitfall in the first one is the temperature unit.

How will I apply this in the equation and do I use Charles's Law?

[Corribus]

Well rather than telling you what equation to use, let's start with making sure you are using thermodynamic equations correctly. What temperature units should you be using if you wanted to apply Charles' Law?

[candysell]

Well rather than telling you what equation to use, let's start with making sure you are using thermodynamic equations correctly. What temperature units should you be using if you wanted to apply Charles' Law?

I would assume Kelvin?

[candysell]

It is Kelvin.  I just solved it.  Thanks for that tip.

[Corribus]

No problem. So, you should have more confidence in the method you are using and just be a little more careful with your units.