[scarpia]

What mass of water and CuSO₄*5H₂0 should we take to prepare 100g of solution with b(CuSO<sub>4)=0.1mol/kg

I don't know what's solvent here (H20 or cooper(II) sulfate pentahydrate)

b(CuSO4)=n(CuSO4)/m(??)</sub>

[Arkcon]

One definition of solvent is ... the one there's more of.  The mass of 0.1 ml mol of copper sulfate is what?  And how does that compare to the amount of water?

[EDIT] edited my typo

[Evaldas]

One definition of solvent is ... the one there's more of.

Except when there's water in the solution. Water is always the solvent in a solution.

[vmelkon]

What mass of water and CuSO₄*5H₂0 should we take to prepare 100g of solution with b(CuSO<sub>4)=0.1mol/kg

I don't know what's solvent here (H20 or cooper(II) sulfate pentahydrate)

b(CuSO4)=n(CuSO4)/m(??)</sub>

100 g solution would have how many mols of CuSO4.5H2O? It would be 0.01 mol of CuSO4.5H2O.
Can you turn that value, 0.01 mol, into grams of CuSO4.5H2O?
Can you the find the mass of water?

[Borek]

Except when there's water in the solution. Water is always the solvent in a solution.

No.

[Evaldas]

Except when there's water in the solution. Water is always the solvent in a solution.

No.

That's what our textbooks say.

[Borek]

Except when there's water in the solution. Water is always the solvent in a solution.

No.

That's what our textbooks say.

Either the textbook is wrong, or it is confusing and you are misreading it.

Benzene can contain up to 0.0363M water. At this concentration you would even have no idea the water is there, it would look just like a pure benzene. Calling it a "water solution" makes no sense.

[Evaldas]

I'm going to e-mail the author of the textbook, because it's exactly what it says

[Evaldas]

<...>

Benzene can contain up to 0.0363M water. At this concentration you would even have no idea the water is there, it would look just like a pure benzene. Calling it a "water solution" makes no sense.

I'm sorry, but I don't really understand what you meant here and I would like some clarification. 1.8g of benzene can dissolve in 1l of water (Wikipedia). Or did you mean that benzene that is sold can contain up to 0.0363 mol/l of water and it would still be sold as pure benzene?
Also, is concentrated (98%) sulfuric acid a water solution or not?
And is water the most polar solvent?

[Borek]

Or did you mean that benzene that is sold can contain up to 0.0363 mol/l of water and it would still be sold as pure benzene?

Any benzene can contain up to 0.0363M of water - and just by looking at it you will never assume it is a water solution. But the definition you listed is "blind" - such benzene contains water, so it is a water solution, even if it clearly is not one.

Also, is concentrated (98%) sulfuric acid a water solution or not?

No. Sulfuric acid is a liquid, miscible with water. When it is 98% of sulfuric acid, I would not call it a water solution.

Note that solvent/solute don't have a precise, widely accepted definitions, so there are some blurry areas where the meaning of both terms is ambiguous.