How can water have a molarity if theres no diff b/w solute and solvent?

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jenzao
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mental block about this please help.
molarity is mols or a substance per Liter of a solution right?
that is, mols of the solute in litres of solution.

1. What is the solution?
2. if its water, then how can you say water has a molarity?
 
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Don't think in terms of solution - ie separate solvent and solute. Concentration is just amount per liter, not per liter of water. Thus you have 55.55 moles of water per liter.
 
Because molarity is how much stuff you have in a certain amount of volume. It doesn't matter if it is water or an HCl solution.
 
So that means that compounds don't necessarily have set molarities right?
for ex, H20 always has mass of 16 + 1 + 1 = 18, and 1 mole is always 18g, but its molarity depends on how many liters of volume 1 mole is contaained in, is that right?

If yes, then why is water said to be 55.5M ??
 
jenzao said:
... molarity depends on how many liters of volume 1 mole is contaained in, is that right?

Not quite. Molarity is how many moles are in 1 liter. For water, it happens to be 55.6. 1 liter of water contains 55.6 moles of water.
 
To be exact, molarity of pure water is 1000/18.02 = 55.51

However, in the 1M solution of acetic acid there is only 946.9 g of water per liter, so its molarity in such solution will be 846.85/18.02 = 52.56
 
Borek said:
To be exact, molarity of pure water is 1000/18.02 = 55.51

However, in the 1M solution of acetic acid there is only 946.9 g of water per liter, so its molarity in such solution will be 846.85/18.02 = 52.56

molarity=no.of moles per volume of soluton in liters
but u did 1000/18.02 how?
 
What is mass of 1L of water?

How many moles in that mass?

--
methods
 
Let me breakdown:
Re: (1L = 1000 cm^3)
water has an approximate density of 1g/cm^3 (temperature dependent)
Therefore, 1000 cm of pure water has an approximate mass of 1000g
Mass of 1 mole of water = 18.02 g
Hence, no. of moles water in 1000 cm^3 of water = Total mass/mass of 1 mole = 1000 g/18.02g per mole = 55.55 moles