Question

Ethyl chloride (c2h5cl) , a substance used as a topical anesthetic, is prepared by reaction of ethylene with hydrogen chloride: c2h4(g) hcl(g)→c2h5cl(g) δh∘ = -72.3 kj .

Answer 1

Ethyl chloride is used as a local anesthetic because its quick evaporation when sprayed as a liquid on the skin produces a cooling effect that numbs the area. This is because the evaporation is an endothermic process that absorbs heat, leading to cooling.

Step-by-step explanation:

Ethyl chloride, with a boiling point of 13 °C, is used as a local anesthetic in medical applications. When applied on the skin as a liquid, it evaporates quickly due to its low boiling point, absorbing heat from the skin in the process. This endothermic phase change causes a cooling effect that numbs the skin. The cooling effect of ethyl chloride involves the consumption of heat from the surrounding environment (in this case, the skin), which is necessary for the liquid to transition to the gas phase. Because endothermic processes take in heat, they result in a decrease in temperature of the surroundings, thus freezing and numbing the sprayed area.