Ideal Gas Law Lab: Finding R with PV = nRT

[mirandasatterley]

For the first part of my lab, I have a graph with pressure(atm) as a function of temperature(K).

For the second part of my lab, I have a graph with pressure(atm) as a function of inverse volume(mL^-1)

For both of these, i am supposed to find the value for R, the gas constant.

So far far part a i have: PV = nRT
P = (nR/V)T (in the form y = mx +b),
So the slope of my graph is nR/V
I also know that n is kept constant, because it was a closed system and 1mol= 22.4L. And that the initial volume is 20mL.
And i think I should I pick two points on the line to find the slope and set that equal to nR/V.

And this is where I'm having trouble, i get some value for the slope, m, so
m = nR/V
R = mV/n, here I'm confused at how to find V and n in order to solve for R.

For part b; PV = nRT
P = (nRT) 1/V
So the slope of my graph is nRT
I did the same thing as part one;
m = nRT
R = m/nT, since T was not chnged, I can do that part, but once again, I am confused by finding n.

 

[Andrew Mason]

For the first part of my lab, I have a graph with pressure(atm) as a function of temperature(K).

For the second part of my lab, I have a graph with pressure(atm) as a function of inverse volume(mL^-1)

For both of these, i am supposed to find the value for R, the gas constant.

So far far part a i have: PV = nRT
P = (nR/V)T (in the form y = mx +b),
So the slope of my graph is nR/V
I also know that n is kept constant, because it was a closed system and 1mol= 22.4L. And that the initial volume is 20mL.
And i think I should I pick two points on the line to find the slope and set that equal to nR/V.

And this is where I'm having trouble, i get some value for the slope, m, so
m = nR/V
R = mV/n, here I'm confused at how to find V and n in order to solve for R.

For part b; PV = nRT
P = (nRT) 1/V
So the slope of my graph is nRT
I did the same thing as part one;
m = nRT
R = m/nT, since T was not chnged, I can do that part, but once again, I am confused by finding n.

As I understand your lab experiment you are doing the following:

1) You keep Volume constant, and take measurements of Pressure at various Temperatures. A plot of P as a function of T should be a straight line P = nRT/V with slope m = nR/V and y intercept b=0.

2) Keeping T constant, take measurements of Volume at various Pressures. A plot of P as a function of 1/V should be a straight line: P = nRT(1/V) with slope m = nRT and y intercept b=0.

In 1) you determine V by measurement. You just have to keep n and V constant while you change the temperature.

In 2) you just have to keep n and T constant as you change the volume.

To find n, you have to weigh the gas. If you use the fact that 1 mole occupies 22.414 L at STP you are indirectly using the known value for R:

R = PV/nT = 101325*.022414/1*273.15 = 8.3145 J/mol K

AM

 

[kyle8921]

Thank you for sharing your lab results with me. It seems like you have a good understanding of the Ideal Gas Law and how to use it to calculate the gas constant, R. In order to solve for R, you will need to know the values of n, the number of moles, and V, the volume.

For part a, you mentioned that n is kept constant and is equal to 1 mole. This means that you can use this value in your calculation for R. As for V, you mentioned that the initial volume is 20mL. This value should be used in your calculation as well. So, your final equation for R should be R = m(20mL)/1 mole.

For part b, the same approach can be used. You mentioned that n is once again constant and equal to 1 mole. This value can be used in your calculation for R. As for V, you mentioned that it is the inverse of volume, so you will need to use the inverse value of the initial volume (20mL) in your calculation. Your final equation for R should be R = m/20mL.

I hope this helps clarify the steps needed to solve for R in both parts of your lab. Keep up the good work in your scientific experiments!