Gas Laws and Thermodynamics questions

[hadroneater]

1) If air contains 1% AR by volume, what is the mass of Argon in a 2L balloon of air at 25 degress celsius?

2) If for a real gas, P = RT(V - b) - a/V^2
where a and b and R are constants, P = pressure, T = temperature and V = volume.
What does a large a value represent in a real gas?

3)A small pond has a layer of ice 1cm thick foating on its surface.
(a) If the air temperature is -10 degrees C, find the rate in cm per hour at which ice is added to the layer. The thermal conductivity of ice is 0.592 W/mK.
(b) How long does it take for a 20cm layer to build up?

Homework Equations

1) pV=nRT Ptotal = p1 + p2...pn

3) H = k*A*dT/L

The Attempt at a Solution

1) I'm not sure if I'm supposed to use the simple addition equation where pressure of argon is just 1% of the total pressure.

2) Obviously the gas would have lesser volume as a increases. But why do non-ideal gases exhibit this pressure drop?

3) heat associated with freezing 1cm^3 water = mL = 0.001g * 334*10^3 = 334J
That's really as far as I got...

 

[Andrew Mason]

The Attempt at a Solution

1) I'm not sure if I'm supposed to use the simple addition equation where pressure of argon is just 1% of the total pressure.

You have to use the fact that a mole of any gas occupies the same volume (if the temperature and pressure are the same). For example, one mole of any gas occupies 22.4 l at STP. This means that the volume occupied by a gas depends on the number of moles of gas ie. the number of freely moving gas molecules (or individual atoms in a monatomic gas such as Argon).

If 1% of the volume is occupied by Argon, then what can you say about the number of Argon atoms compared to the number of other air molecules?

2) Obviously the gas would have lesser volume as a increases. But why do non-ideal gases exhibit this pressure drop?

I think you meant "lesser pressure as a increases". The pressure drop is due to the attraction between molecules - this requires energy to separate the molecules.

The third question is not copied correctly. What is the rate of ice build-up?

AM

 

[hadroneater]

The rate in the third question isn't given. It's actually supposed to say "find the rate in cm per hour". My bad.

 

[Andrew Mason]

The rate in the third question isn't given. It's actually supposed to say "find the rate in cm per hour". My bad.

Ok. The with that change the language now makes grammatical sense. But the question doesn't make sense:

3)A small pond has a layer of ice 1cm thick foating on its surface. (a) If the air
temperature is 10 degrees C, find the rate in cm per hour at which ice is added to the layer. The thermal conductivity of ice is 0.592 W/mK. (b) How long does it take for a 20cm layer to
build up?[/b]

Why would ice build up at +10C?

AM

 

[hadroneater]

Again...my fault. It's supposed to be -10degrees. My bad.