00:01
A cylinder contains 0 .1 moles of an ideal gas, monotomic gas.
00:05
Initially, the gas is at 1, 10 of the 5 pascal, occupies a volume of 2 .5 to 10 of the minus 3 meter cubed.
00:11
Find the initial temperature of the gas.
00:17
If the gas is allowed to expand to twice the volume, find a final temperature.
00:22
And if the gas is allowed to expand it twice, it's an initial volume, find the temperature in kelvin's and pressure the gas if the expansion is isothermal, isylbaric, or adiabatic.
00:31
Okay.
00:32
Let's write down what's given to us.
00:34
And start from there.
00:36
So you have the number of moles, 0 .1 moles, and you have the initial pressure, not 2, but 1 times 10 to the 5th pascal's, rdnsi, and i would need to convert.
01:03
V initial is 2 .5 times 10.
01:08
To the minus 3 meters cubed.
01:13
And our goal first a is to get the initial temperature.
01:16
This is an application of the ideal gas law.
01:19
Pv equals nrt.
01:21
If you rearrange that, then you get t is pv over nr.
01:27
And so that's 1 times 10 to the 5 times 2 .5 times 10 to the minus 3 meter cubed pascal's.
01:39
Divided by n, which is 0 .1, and then r8 .3 .1.
01:46
And if you plug that into a calculator, i'm going to double check that what i did was right.
01:57
One second.
02:03
If you plug that into a calculator and i just checked my calculations, you get 301 kelvin.
02:11
So now part b, i'm going to section this off because it might get a little crowded.
02:17
So i'm not going to write out the full calculation.
02:19
I'm just going to say things out loud.
02:21
So they're asking you to consider that your v final equals twice v initial under certain condition.
02:31
So the first condition is isothermal.
02:35
So that means p, so you have the ideal gas law.
02:41
So if t stays the same, let's ask what else stays the same? so t stays the same, r stays the same because that's a constant.
02:49
N is presumed to stay the same.
02:52
So that means pv has to say the same.
02:54
So then you can say p initial v initial equals p final, t final.
03:01
So in general, you can kind of just take whatever stays the same, put it on one side of the equation, and what changes to put it on the other side of the equation, and then say that that side is constant.
03:12
And it looks like i wrote, hold on, i think i wrote t final instead of v final.
03:18
Let me correct that.
03:27
Okay, p -final v final.
03:32
Great.
03:32
And so you can see that if the volume final goes up by a factor of two, then the pf has to go down by a factor of two to keep this product the same.
03:43
So then you get p -final is equal to half of the initial, which is 0 .5 times 10 to the 5 -pascals.
03:53
And then i'll go ahead and label this one and then the next part two and then i'll do three over here...