Thermodynamics/Ice Cream

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Question
I was wondering how ice cream is sometimes frozen with salt and water. I know that salt lowers the temperature of water. I looked up answers online, but I couldn't find the in-depth answer I wanted. Thanks!

Answer
Hi Elizabeth,

The equation for dilute solutions is called Blagden's Law.

dTf = Kf * b * i

Where:-
dTf is the depression of the freezing point in K.
Kf is the cryoscopic constant (1.853 K.kg/mol for water).
b is the molality, mole of solute per kg of solvent.
i is the van't Hoff factor. The number of ions per individual molecule of solute. (2 for NaCl
and three, for example, for CaCl2).

I hope this helps
Best wishes,
Kevin.  

Thermodynamics

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Kevin

Expertise

Thermodynamics, chemistry, chemical reactions, kinetics, chemical reaction safety, dust explosion technology, static electricity. General science.

Experience

Over 40 years experience as a practicing thermochemist in industry. Head of the fire and explosion laboratory of a major European chemical company (Ciba-Geigy). Now retired.

Organizations
Institute of Chemical Engineers. Royal Society of Chemistry.

Education/Credentials
Chartered Chemist, Member of the Royal Society of Chemistry (C.Chem MRSC). Msc Sheffield.

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