Chemistry Help

[us3rnotfound]

In ice-cream making, the temperature of the ingredients is kept below 0.0 oC in an ice-salt bath. Assuming that NaCl dissolves completely and forms an ideal solution, what mass (in grams) of it is needed to lower the melting point of 5.5 kg of ice to ?5.0 oC?

I tried the delta T = Kf*m equation...but for some reason it's wrong. What am I doing wrong?

 

[Toastedlightly]

did you incorporate the # of particles? There are 2 per "molecule" of salt.

 

[us3rnotfound]

Thanks a lot Toastedlightly :beer:

hmm....now a new question arises...

"De-icing salt" is used to melt snow and ice on streets. The highway department of a small town needs to decide whether to buy NaCl or CaCl2 for the job. The town can obtain NaCl for $0.28/kg this winter season. What is the maximum the town should pay for CaCl2 ($/kg) to be cost effective and get the same temperature lowering effect as 1 kg NaCl?

Any tips on how to do this one?

 

[AgaBoogaBoo]

have you compared freezing temperatures for both?

 

[Ika]

CaCl2 dissociates into three particles, while NaCl dissociates into two. Take this into account when calculating the cost-effectiveness.

 

[SociallyChallenged]

Originally posted by: Aflac
CaCl2 dissociates into three particles, while NaCl dissociates into two. Take this into account when calculating the cost-effectiveness.

I miss this kind of Chemistry, lol.