Trouton\\\'s rule states that the molar enthalpy of vaporization of a liquid tha

Question

Trouton's rule states that the molar enthalpy of vaporization of a liquid that does not have strong molecular interactions such as hydrogen bonding or ion-ion attractions is given by where Tb is the normal boiling point of the liquid in kelvins. a) Apply Trouton's rule to estimate the value of ?Hvap for these compounds.   Tb values are given in the "Hint" below.

Trouton's rule states that the molar enthalpy of vaporization of a liquid that does not have strong molecular interactions such as hydrogen bonding or ion-ion attractions is given by AHp 85 J-K .molT where Tb is the normal boiling point of the liquid in kelvins a) Apply Trouton's rule to estimate the value of AHvap for these compounds b values are given in the "Hint" below chloromethane water hydrogen sulfide Number Number Number kJ/ mol k.J / mol k.J/ mol b) Compared to the accepted Hap values (given in the ''Hint") what is the percentage error in each case? chloromethane water hydrogen sulfide Number Number Number

Explanation / Answer

Answer –

a) Given, Trouton’s rule formula

Hvap = (85 J.K-1.mol-1) Tb

Now we need to first find out the normal boiling point in Kelvin of each one

Normal boiling point of chloromethane = 248.95 K

Normal boiling point of water = 373.15 K

Normal boiling point of hydrogen sulfide = 213.15 K

So the Hvap as bellow –

For chloromethane –

Hvap = (85 J.K-1.mol-1) * 248.95 K

          = 21160.75 J/mol

          = 21.161 kJ/mol

For water –

Hvap = (85 J.K-1.mol-1) * 373.15 K

          = 31717.75 J/mol

          = 31.717 kJ/mol

For hydrogen sulfide

Hvap = (85 J.K-1.mol-1) * 213.15 K

          = 18117.75 J/mol

          = 18.117 kJ/mol

b) The standard value of the Hvap for the given three as below –

Hvap for chloromethane = 21.40 kJ/mol

Hvap for water = 40.65 kJ/mol

Hvap for hydrogen sulfide = 18.67 kJ/mole

So the percent error of each one as follow –

Percent error of chloromethane = 21.40 -21.161 / 21.40 *100 %

                                               = 1.12 %

Percent error of water = 40.65 -31.717 /40.65 *100%

                                = 21.97 %

Percent of hydrogen sulfide = 18.67 -18.117 / 18.67 *100%

                                         = 2.96 %

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