Predict Which Of The Following Compounds Follow Trouton’s Rule
Trouton’s rule is a rule that states that the heat of vaporization of liquids is approximately the same, regardless of the size of the molecule. This rule was proposed by William Trouton in the 1880s and is based on the observation that the enthalpy of vaporization of some substances varies inversely with the molecular weight. Thus, Trouton’s rule can be used to predict the enthalpy of vaporization of a liquid by multiplying the molecular weights of two different liquids. In this article, we will use Trouton’s rule to predict which of the following compounds follow the rule.
Molecular Weights of Compounds
- Ethanol: 46.07 g/mol
- Methanol: 32.04 g/mol
- Propanol: 60.10 g/mol
- Butanol: 74.12 g/mol
Calculating the Heat of Vaporization
The heat of vaporization can be calculated using Trouton’s rule by multiplying the molecular weights of the compounds. Thus, if we multiply the molecular weight of ethanol (46.07 g/mol) with that of methanol (32.04 g/mol) then we get 1,472.8 /mol. The heat of vaporization of this compound should be approximately the same as that of propanol (60.10 g/mol) multiplied by butanol (74.12 g/mol) which is 4,446.5 /mol.
Conclusion
From the calculations, it is seen that the heat of vaporization of ethanol and methanol (1,472.8 /mol) is much lower than that of propanol and butanol (4,446.5 /mol). Therefore, these compounds do not follow Trouton’s rule.
The rule is based on the observation that molecules with higher molecular weights have a lower enthalpy of vaporization, so the rule may not be applicable to all substances. It is important to remember that Trouton’s rule is just an approximation and it can be used to predict the enthalpy of vaporization of liquids, but it should not be used for precise calculations.