Molality

[j.i.s.f.]

A concentrated sulfuric acid solution is 65.0% H2SO4 by mass and has a density of 1.55 g/mL at 20 degrees Celsius. (MW is 98.0 g/mol). The molality of the solution it?

I understand how to do it otherwise, but the density is throwing me off

[kingchemist]

65% by mass means 65g H2SO4 per 100g of solution

I don't think you need the density which would be needed if the concentration was given in grams/volume and you would then have to convert volume to mass.

65g H2SO4 per 100g of solution means 65g H2SO4 and 100-65g = 35g of water.

Moles H2SO4 = 65/98.0

Molality = moles/mass of solvent in kg = (65/98.0)/0.035