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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: daylees on September 22, 2010, 10:51:32 PM

Title: How do i find molality and mass precent given molarity and density?
Post by: daylees on September 22, 2010, 10:51:32 PM

An aqueous KNO₃ solution is made using 87.8g of KNO₃ diluted to a total solution volume of 1.60L.

Molarity =0.543M
calculate molality and mass precent (density =1.05g/mL)

i don't even know where to begin.

Title: Re: How do i find molality and mass precent given molarity and density?
Post by: opti384 on September 23, 2010, 02:15:06 AM

What can you learn from the Molarity = 0.543M, density, and the total solution volume?

Title: Re: How do i find molality and mass precent given molarity and density?
Post by: skbuncks on September 24, 2010, 07:49:56 AM

It can help if you express the units of all the terms present.

Molarity = mol/L
Density = g/ml (or Kg/L)
Molality = mol/kg (mols solute/kg solvent)
Mass percent =  g/g %

So to calculate the molality you will need to know the mols of KNO3 and the mass of solvent (not the total mass).

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