How come water has a concentration?

[scilearner]

Ok density of water is 1000 g/ 1 L

 

I don't know isn't this 1 L composed completely of water. This is confusing me. Do find the concentration you have to find the moles and divide by 1 L. 1000/18=55 M . I thought concentration of pure water you can't find because the solution is complete water. I hope you understand what I mean. Thanks

[insane_alien]

the concentration is the number of mols per unit volume right?

 

well, pure water is 55 mol/L

 

simple.

 

its fractional composition is 1 if you care. but there really is no reason why a pure substance can't have a concentration at all, its just equivalent to its molar density.

[Mr Skeptic]

And what if you vaporize the water, increasing the volume but decreasing the density? Then your pure water will be less concentrated.

[John Cuthber]

Just for the record, to two significant figures 1000/18= 56 not 55.