The cooling effect of alcohol on the skin is due to its evaporation. Calculate t

Question

The cooling effect of alcohol on the skin is due to its evaporation. Calculate the heat of vaporization of ethanol (ethyl alcohol). C_2H_5OH. C_2H_5OH(l) rightarrow C_2H_5OH(g); DeltaHdegree = ? The standard enthalpy of formation of C_2H_5OH(l) is -277.7 kJ/mol and that of C_2H_5OH(g) is -235.4 kJ/mol. 6.78 Carbon tetrachloride, CCI_4, is a liquid used as an industrial solvent and in the preparation of fluorocarbons. What is the heat of vaporization of carbon tetrachloride? CCI_4(l) rightarrow CCI_4(g); DeltaHdegree = ? Use standard enthalpies of formation (Table 6.2).

Explanation / Answer

6.77)

consider the given reaction

C2H5OH (l) --> C2H5OH (g)

we know that

dHo rxn = dHof products - dHof reactants

so

dHo rxn = dHof C2H5OH (g) - dHof C2H5OH (l)

using given values

we get

dHo rxn = -235.4 - ( -277.7)

dHo rxn = 42.3

so

dHo for the given reaction is 42.3 kJ/mol

6.78)

CCl4(l) ---> CCl4 (g)

in this case

dHo rxn = dHof CCl4 (g) - dHof CCl4 (l)

using standard enthalpies

we get

dHo rxn = -95.98 + 135.4

dHo rxn = 39.42

so

dHo for this reaction is 39.42 kJ/mol

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