My Math Forum  

Go Back   My Math Forum > Science Forums > Chemistry

Chemistry Chemistry Forum


Reply
 
LinkBack Thread Tools Display Modes
March 26th, 2017, 02:52 AM   #1
Member
 
Joined: May 2016
From: Ireland

Posts: 92
Thanks: 1

ideal gas

Out of the gases hydrogen, nitrogen, chlorine, and helium, which shows behaviour closest to an ideal gas?

I've been told the answer is helium because there are no attractive forces between helium atoms. Would there not be Van der Waals forces though? Also, would hydrogen just have as little attractive forces as well?

Last edited by skipjack; March 26th, 2017 at 07:39 AM.
markosheehan is offline  
 
March 26th, 2017, 03:51 AM   #2
Senior Member
 
Joined: Jun 2015
From: England

Posts: 566
Thanks: 146

Van der Waals forces arise because the atoms or molecules are 'unbalanced' or unsymmetrical in their electrical distribution in space.
They are still electrically neutral, it does not mean that they are electrically charged.
It means.
We consider the positive nucleus as fixed and the negative electron or electrons as whizzing around the nucleus.
As they whiz around, if there are an even number of electrons, the individual attractions between the nucleus and the electrons cancels out on average.
But if there are an odd number of electrons this is not possible.

Hydrogen has one electron, helium has two.

But this is only one part of the reason for the deviation from the ideal gas laws.

The other part is due to the fact that the atoms/molecules occupy physical space.
The bigger this space, the greater this deviation component is.

Van der Waals introduced a correction factor in his equation of state for this as well.

Last edited by skipjack; March 26th, 2017 at 08:05 AM.
studiot is offline  
March 26th, 2017, 07:06 AM   #3
Member
 
Joined: May 2016
From: Ireland

Posts: 92
Thanks: 1

So which is it - hydrogen or helium?
More temporary dipoles form in helium, so it's less close to an ideal gas.

Because hydrogen has only 1 electron so it's smaller, so molecules are more widely spaced. Therefore it's closer to being an ideal gas. The right answer is helium though. Now I am even more confused than originally.

Last edited by skipjack; March 26th, 2017 at 07:33 AM.
markosheehan is offline  
March 26th, 2017, 07:46 AM   #4
Senior Member
 
Joined: Jun 2015
From: England

Posts: 566
Thanks: 146

Hydrogen is a molecule, which is larger than a helium atom.

Helium does not readily form molecules, even with itself.
studiot is offline  
March 27th, 2017, 02:38 AM   #5
Senior Member
 
Joined: Apr 2014
From: Glasgow

Posts: 1,965
Thanks: 640

Math Focus: Physics, mathematical modelling, numerical and computational solutions
Quote:
Originally Posted by markosheehan View Post
So which is it - hydrogen or helium?
More temporary dipoles form in helium, so it's less close to an ideal gas.

Because hydrogen has only 1 electron so it's smaller, so molecules are more widely spaced. Therefore it's closer to being an ideal gas. The right answer is helium though. Now I am even more confused than originally.
I'm not sure I agree that hydrogen behaves more like an ideal gas, because it can form diatomic hydrogen (H$\displaystyle _2$), therefore giving it a vibrational degree of freedom.

Helium is a noble gas. The noble gases are, broadly speaking, the most unreactive of all the elements and very rarely participate in chemical reactions. They always have exactly enough electrons to fill their outer electron shells, so they are already in their most stable state with regards to the possibility of combination with other atoms of the same kind.
Benit13 is offline  
Reply

  My Math Forum > Science Forums > Chemistry

Tags
gas, ideal



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
the zero set of an ideal rayman Abstract Algebra 1 January 29th, 2014 12:35 AM
Ideal in z(x) alejandrofigueroa Abstract Algebra 0 November 4th, 2013 10:11 AM
ideal Joolz Abstract Algebra 3 September 20th, 2012 06:47 PM
ideal ely_en Real Analysis 0 March 4th, 2012 12:22 PM
Ideal HairOnABiscuit Abstract Algebra 3 December 12th, 2009 02:11 PM





Copyright © 2017 My Math Forum. All rights reserved.