Using the tables of enthalpies of formation and entropies of formation, estimate the boiling point for the following liquid: methanol (CH3OH), ethanol (C2H5OH) and acetic acid (CH3COOH). compare to their tabled boiling points.
how would i go about working this question?
table values:
mbp methanol- 65.15 degrees C
mbp ethanol - 78.5 degrees C
mbp acetic acid- 117.9 degrees C
To estimate the boiling point of a liquid using the tables of enthalpies of formation and entropies of formation, you need to consider the principles of thermodynamics. The boiling point of a liquid depends on the balance between the energy needed to break the intermolecular forces holding the liquid together (enthalpy of vaporization) and the dispersal of molecules in the gas phase (entropy).
Here are the steps to work through this question:
1. Determine the chemical equation for the vaporization of the liquid. For the liquids in question, methanol (CH3OH), ethanol (C2H5OH), and acetic acid (CH3COOH), the vaporization equations are:
CH3OH(l) -> CH3OH(g)
C2H5OH(l) -> C2H5OH(g)
CH3COOH(l) -> CH3COOH(g)
2. Use the given tables of enthalpies of formation for each substance to find the enthalpy of vaporization (ΔHvap) for each equation. The enthalpy of vaporization is the difference in enthalpies between the vapor and liquid phases.
3. Use the given tables of entropies of formation for each substance to find the entropy of vaporization (ΔSvap) for each equation. The entropy of vaporization is the difference in entropies between the vapor and liquid phases.
4. Calculate the Gibbs free energy change (ΔG) for each equation using the equation: ΔG = ΔH - TΔS, where T is the temperature in Kelvin.
5. The boiling point occurs when ΔG = 0, which means the vapor and liquid phases are in equilibrium. Therefore, you need to solve for the boiling point temperature (T).
6. Compare the calculated boiling point temperature with the tabled boiling point for each substance and analyze the differences.
By following these steps, you can estimate the boiling points of methanol, ethanol, and acetic acid using the given tables of enthalpies and entropies of formation.