[uzi4u2]

okay so this is the question :
0.15g urea ( molar mass 60 delton ) is dissolved in 25g water . what is the freezing point depression of the solution ? the molal freezing point Kf of water is 1.85

now the formula is     dT=Kf*C*I

so what i did was     0.15/60   in order to get the number of moles in 1000g
this gave me   2.5x10-3    but this is in 1000g  so i need it in 25g so
 
                                           2.5x10-3 ... 1000
                                                      x.... 25 
                           x=  6.25x10-3   

and now i take this and put it in the formula instead of C   but it dosent come out good :\
any ideas on what i am doing wrong ?

[Yggdrasil]

To calculate the concentration, you need to figure out the number of moles then divide that by the volume of your solution, so its:

0.15g / 60 g/mol = 2.5x10^-3 mol (you did this correctly) but,
concentration = 2.5x10^-3 mol / 25g

[uzi4u2]

oo i see so it will be      x/25*1000  and what i will get from it i will put in the equation ! great

thanks