the molality of a calcium fluoride solution is 2.33 m. If the solution is prepared with 125 mL of water, how many grams of calcium fluoride were added to the solution?

Question

jfraser · Answer

what are the units of molALity? (not molARity)

anonymous · Answer

molality= mol solute/ kg solvent

jfraser · Answer

so we know the molality, and we know the volume of solvent. What do we also know about the density of water?

anonymous · Answer

the density of water is 0.992g/mL

jfraser · Answer

so we have a way to convert the volume of water used into a mass:$$volume H_2O * (\frac{mass}{volume})$$
that mass of 125mL of water is now the proper term to use in the molality equation:

$$molality = \frac{mol solute}{kg solvent}$$
the molality we know, and now we know the mass of solvent used. Find the moles of solute by rearranging, and then convert that moles into mass using the molar mass of calcium fluoride

anonymous · Answer

so the mass of 125mL is 124g?

jfraser · Answer

essentially, yes. we usually just call the density of water 1g/mL, for really easy conversions

anonymous · Answer

so the final answer would be .0289 grams?

jfraser · Answer

that's not what i get

jfraser · Answer

do it one step at a time

anonymous · Answer

I did. What did you get?