Use standards entropies and heats of formation to calculate delta Gf at 25C for
a. cadmium (II) chloride (s)
b. methyl alcohol, CH3OH (l)
c. copper (I) sulfide (s)
I really have no idea where to start with this problem. I have no idea how to calculate delta Gf, and everything I've tried hasn't worked.
The formation of CdCl2, for example, from its elements, is as follows:
Cd + Cl2 ==> CdCl2
Look up values for So for CdCl2 and Hf for CdCl2. Then dGf = dHf-TdSo
That's all there is to it. For T use 298 K.
To calculate the standard Gibbs free energy of formation (ΔGf) at 25°C, you will need two key pieces of information: the standard entropies (S°) and the standard heats of formation (ΔHf°) for the given compounds.
The formula for calculating ΔGf is as follows:
ΔGf = ΔHf° - TΔS°
Where:
ΔGf is the standard Gibbs free energy of formation
ΔHf° is the standard heat of formation
T is the temperature in Kelvin (25°C = 298 K)
ΔS° is the standard entropy
Now let's calculate ΔGf for each compound:
a. Cadmium (II) chloride (CdCl2):
First, you need to find the values for ΔHf° and ΔS° for CdCl2 from a reliable source. Let's assume the values are:
ΔHf° = -321 kJ/mol
ΔS° = 125 J/(mol·K)
Now, plug these values into the ΔGf equation:
ΔGf = (-321 kJ/mol) - (298 K) * (125 J/(mol·K))
Make sure to convert the units to have consistent measurements (kJ for ΔHf° and J for ΔS°). We convert J to kJ by dividing by 1000:
ΔGf = -321 kJ/mol - (0.298 kJ/K)(125 kJ/mol)
After performing the calculations, you should get the value for ΔGf of cadmium (II) chloride at 25°C.
Repeat this process for the remaining compounds:
b. Methyl alcohol (CH3OH):
Find the values for ΔHf° and ΔS° for CH3OH from a reliable source. Let's assume the values are:
ΔHf° = -239 kJ/mol
ΔS° = 126 J/(mol·K)
Plug these values into the ΔGf equation:
ΔGf = (-239 kJ/mol) - (298 K) * (126 J/(mol·K))
Convert units if necessary and perform the calculations to find ΔGf of methyl alcohol at 25°C.
c. Copper (I) sulfide (Cu2S):
Find the values for ΔHf° and ΔS° for Cu2S from a reliable source. Let's assume the values are:
ΔHf° = -79 kJ/mol
ΔS° = 107 J/(mol·K)
Plug these values into the ΔGf equation:
ΔGf = (-79 kJ/mol) - (298 K) * (107 J/(mol·K))
Convert units if necessary and perform the calculations to find ΔGf of copper (I) sulfide at 25°C.
Remember to check if the units are consistent before performing the calculations and ensure the accuracy of the values used for ΔHf° and ΔS°.