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 points of methanol, ethanol, and acetic acid using the tables of enthalpies of formation and entropies of formation, we need to consider the relationship between these thermodynamic properties and boiling point.
First, let's understand how enthalpy of formation and entropy of formation affect boiling point:
1. Enthalpy of Formation (ΔHf): It represents the change in enthalpy when one mole of a compound is formed from its constituent elements in their standard states. A higher enthalpy of formation generally indicates stronger intermolecular forces, which tend to raise the boiling point.
2. Entropy of Formation (ΔSf): It measures the change in disorder or randomness associated with the formation of one mole of a compound. A higher entropy of formation indicates greater molecular disorder, which tends to lower the boiling point.
Now, let's compare the estimated boiling points to their tabled boiling points for methanol, ethanol, and acetic acid:
1. Methanol (CH3OH):
- Prepare the balanced chemical equation for the combustion of methanol: CH3OH(l) + 3/2O2(g) → CO2(g) + 2H2O(l).
- Look up the enthalpy of formation (ΔHf) and entropy of formation (ΔSf) values for methanol in the tables.
- Calculate the change in Gibbs free energy (ΔG) using the equation: ΔG = ΔH - TΔS, where T is the temperature in Kelvin.
- Estimate the boiling point by finding the temperature at which ΔG becomes zero.
- Compare the estimated boiling point with the tabled boiling point.
Repeat the same procedure for ethanol (C2H5OH) and acetic acid (CH3COOH) to estimate their boiling points.
It's important to note that the estimated boiling points may not match the tabled values exactly due to simplified calculations and assumptions made in this estimation method.