Question

Liquid Boiling point (K) Enthalpy of vaporization (kJ/mol) benzene 353.1 30.72 toluene 383.6 33.18 nonane 423.8 37.18 chloroform 334.2 29.24 ethanol 351.3 38.56 water 373 40.65 Predict which of the following compounds follow Trouton's rule. Check all that apply. View Available Hint(s) Check all that apply. ethanol water nonane benzene chloroform toluene Submit

Answer 1

(a) The compound benzene follow the Trouton's rule.

(b) The compound toluene follow the Trouton's rule.

(c) The compound nonane follow the Trouton's rule.

(d) The compound chloroform follow the Trouton's rule.

(e) The compound ethanol does not follow the Trouton's rule.

(f) The compound water does not follow the Trouton's rule.

Explanation :

Trouton's rule : According to this rule, the molar entropy of vaporization should be constant that means,

`\Delta S_(vap)=85-88J/K.mole`

Formula used :
`\Delta S=(\Delta H_(vap))/(T_b)`

Now we have to determine the molar entropy of vaporization for the following compounds.

(a) For Benzene:

Boiling point = 353.1 K

Enthalpy of vaporization = 30.72 kJ/mole = 30720 J/mole

`\Delta S=(30720J/mole)/(353.1K)=87.00J/K.mole`

Thus, this compound is follow the Trouton's rule.

(b) For Toluene:

Boiling point = 383.6 K

Enthalpy of vaporization = 33.18 kJ/mole = 33180 J/mole

`\Delta S=(33180J/mole)/(383.6K)=86.49J/K.mole`

Thus, this compound is follow the Trouton's rule.

(c) For Nonane:

Boiling point = 423.8 K

Enthalpy of vaporization = 37.18 kJ/mole = 37180 J/mole

`\Delta S=(37180J/mole)/(423.8K)=87.73J/K.mole`

Thus, this compound is follow the Trouton's rule.

(d) For Chloroform :

Boiling point = 334.2 K

Enthalpy of vaporization = 29.24 kJ/mole = 29240 J/mole

`\Delta S=(29240J/mole)/(334.2K)=87.49J/K.mole`

Thus, this compound is follow the Trouton's rule.

(e) For Ethanol:

Boiling point = 351.3 K

Enthalpy of vaporization = 38.56 kJ/mole = 38560 J/mole

`\Delta S=(38560J/mole)/(351.3K)=109.76J/K.mole`

Thus, this compound is not follow the Trouton's rule.

(f) For Water:

Boiling point = 373 K

Enthalpy of vaporization = 40.65 kJ/mole = 40650 J/mole

`\Delta S=(40650J/mole)/(373K)=108.98J/K.mole`

Thus, this compound is not follow the Trouton's rule.