What are the enthalpy, entropy, and free energy for the hydrogenation of ethene (C2H4) to ethane (C2H6) at 25 degrees. Is this a spontaneous process and how can you tell?
What do you need help with on this. I'm sure it isn't all of the problem.
Write the equation and balance it.
dHrxn = (n*dHf products)-(n*dHf reactants)
dSrxn = (n*dSo products)-(n*dSo reactants)
dGrxn = dHrxn -TdSrxn
Spontaneity is when dG is negative.
To determine the enthalpy (ΔH), entropy (ΔS), and free energy (ΔG) for the hydrogenation of ethene to ethane, you can consult standard thermodynamic data. This data is often given in tables or online databases.
To answer the first part of your question, we need to find the ΔH, ΔS, and ΔG values for the reaction. Let's break it down into two steps:
Step 1: The reaction equation for the hydrogenation of ethene to ethane is:
C2H4 (g) + H2 (g) → C2H6 (g)
Step 2: Find the standard thermodynamic data for each component involved in the reaction. These data values are generally given at standard conditions of 25 degrees Celsius (298 K) and 1 atmosphere pressure.
The enthalpies of formation (ΔHf) for C2H4 (g) and C2H6 (g) can be found in the thermodynamic tables. The ΔHf for substances in their standard states is defined as zero. Therefore, you need to subtract the ΔHf values for the reactants from the products.
The standard enthalpy change (ΔH°) for the reaction can then be calculated using Hess's Law, which states that the sum of the enthalpy changes for a series of reactions is equal to the overall enthalpy change.
Similarly, the standard entropy change (ΔS°) can be calculated by subtracting the sum of the reactant entropies from the sum of the product entropies.
Finally, the standard free energy change (ΔG°) can be calculated using the equation ΔG° = ΔH° - TΔS°, where T is the temperature in Kelvin.
Now, regarding the second part of your question, to determine whether the process is spontaneous or not, you need to consider the sign of ΔG. If ΔG is negative, the process is spontaneous. If ΔG is positive, the process is non-spontaneous. If ΔG is zero, the process is at equilibrium.
Therefore, calculate ΔG° using the given values and temperature. If ΔG° is negative, then the hydrogenation of ethene to ethane at 25 degrees Celsius is a spontaneous process.