# Thread: Molar density?

1. A rather stupid question: what is the difference between molar density and concentration? Do they mean the same, and if not what is the difference?  2.

3. molar density, do u mean moalr volume? http://en.wikipedia.org/wiki/Molar_volume

conentration is expressed in mol/litre, and is in a solution, aquatic mostly

while molar volume is litre/mol and is a propety of a substance, gases often have the same here under same circumstances  4. Actually I mean a variable described as ρ=n/V.

A quotation from my book ('Thermodynamics, Statistical Thermodynamics & Kinetics' by Engel & Reid):
"...we consider a dilute gas under conditions in which the ideal gas law of Equation (1.1) describes the relationship among P, T and the molar density ρ=n/V with sufficient accuracy: P=ρRT..." <- that is the Equation (1.1)

Zelos said that concentration is used with solutions. Is this just some thing that with solutions we refer to concentration and with gases to molar density?   5. hi scythe,
you mentioned it: molar density ρ=n/V

The is n and N. The small letter (n) denotes the number of moles. While the capital one (N) means the number of parts (molecules, atoms etc...).
So a molar density is the number of moles of something per volume.

example:
I make a dilution of 3 mole glucose in 1 liter water. The molar density is 3 mol/L while the number density is: 3 x 6.022x10^23 molecules glucose per liter.  Bookmarks
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