Answer to Question #184943 in General Chemistry for Kennedy

Question

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Salt is often used to melt ice and snow on roads in the winter and the temperature right now is -4500°C. How much NaCl (complete dissociation) would be necessary to melt 1000 kg of ice by bringing down the freezing temperature to -4500°C? Solved and Explain briefly.

Answer 1

When added to ice, salt first dissolves in the film of liquid water that is always present on the surface, thereby lowering its freezing point below the ices temperature. Ice in contact with salty water therefore melts, creating more liquid water, which dissolves more salt, thereby causing more ice to melt, and so on. As the temperature drops, salt's effectiveness slows to the point that when you get down near 10 degrees and below, salt hardly works at all.