freezing point depression

[JustwantDDS]

so the freezing point depression equation is delta Tf= - ikfm

but if the Kf is given as a - do we need to put the - on the outside
the reason i ask is this:

A solution contains 1.5 mol of solute which is dissolved in 300 g of water, what is the fp of the solution? kf of water is -1.86

deltaTf= (1)(-1.86)(5m) = ~ -10 if we put - in front the equation it would be +10

and to find Fp = 0+10...would be +10 but the answer is -10

if the - is out of the front of the equation it would be -10 , 0+ -10= -10


i guess you could conceptually say, freezing point DEPRESSION so it has to be subtracted from 0 , or less than 0 if your solvent is water...
but anyway.............

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[toothhornet88]

so the freezing point depression equation is delta Tf= - ikfm

but if the Kf is given as a - do we need to put the - on the outside
the reason i ask is this:

A solution contains 1.5 mol of solute which is dissolved in 300 g of water, what is the fp of the solution? kf of water is -1.86

deltaTf= (1)(-1.86)(5m) = ~ -10 if we put - in front the equation it would be +10

and to find Fp = 0+10...would be +10 but the answer is -10

if the - is out of the front of the equation it would be -10 , 0+ -10= -10


i guess you could conceptually say, freezing point DEPRESSION so it has to be subtracted from 0 , or less than 0 if your solvent is water...
but anyway.............

You answered your own question. You put the negative on the outside which will give you 10. Then you simply subtract it from 0 to get -10