Posted by Eddie on .
A 23.6 molar solution of formic acid (methanoic acid) has a density of 1.16 g/ml. The molar mass of H, C, and O are 1g/mol, 12g/mol and 16 g/mol, respectively. What is the molality of this solution?
A molality is the number of moles of solute dissolved in one kilogram of solvent.
molar mass for HCOOH = 2*1+12+2*16=46
(more accurate value = 46.03)
A litre of the solution contains 23.6 moles, or 1085.6 g of the pure acid, and has a total mass of 1000*1.16=1160 g.
The mass of solvent (water) is therefore 1160-1085.6=74.4.
The molality is 23.6*(1000/74.4) = 317 m
Note: Formic acid is a liquid at room temperature, and is miscible with water.
That is really right