chemistry
posted by Nick on .
A dilute sulfuric acid solution that is 3.39 molality H2SO4 has a density of 1.18 g/mL. How many moles of H2SO4 are there in 375 mL of this solution?

3.39 m = 3.39 moles (332.22 g) + 1 kg solvent.
Mass of solution = 332.22g + 1,000g = 1332.22 grams.
375 mL has a mass of what?
mass = volume x density = 375 mL x 1.18 g/mL = 442.5 grams.
g solute in 375 mL = 332.22g x (442.5/1332.22) = 110.35 g which is 110.35/98 = 1.126 moles H2SO4.
Does that sound reasonable? How much solvent do we have in that 442.5 g. That will be 442.5110.35 = 332.15 g
and 1.126 mole/0.33215 kg = 3.39 m so I think it is reasonable. 
A couple of things I forgot to mention.
1. I used 98 for the molar mass of H2SO4. That may not be close enough for you so you need to through the calculations and adjust numbers as appropriate.
2. I used too many significant figures and you need to adjust them. The final answer should have no more than 3.