Ethyl chloride, C2H5Cl, is used as a local anesthetic. It works by cooling tissue as it vaporizes; its heat of vaporization is 26.4 kJ/mol. How much heat could be removed by 15.0 g of ethyl chloride?

Question

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Answer 1

The heat used to vaporize the ethyl chloride comes from the tissue that it is in contact with. We know the amount of heat removed is 26.4 kJ / mole of ethyl chloride. So first we will determine how many moles of ethyl chloride we have.

Molar mass ethyl chloride = 64.51 g/ mol

Moles ethyl chloride = 15.0 g x 1 mol/64.51 g = 0.233 moles

Now we can determine heat removed from the tissue.

0.233 moles x 26.4 kJ/mole = 6.14 kJ of heat removed

The value of 6.14kJ should have a negative sign but since we said heat is removed that negative sign it’s implied.