DrBob222 PLEASE HELP
Hf of CO2 = -393.5 kJ/mol
Hf of H2O = -285.8 kJ/mol
The combustion reaction for benzoic acid C6H5CO2H(s) + 15/2 O2(g) →
7 CO2(g) + 3 H2O(ℓ) has ∆H0 = −3226.7 kJ/mole. Use Hess’s Law to calculate ∆H0f for benzoic acid.
1. −698.1 kJ/mol
2. −348.6 kJ/mol
3. −1609 kJ/mol
4. No choice is correct.
5. −237.4 kJ/mol
6. −385.2 kJ/mol
I made several typos. Here is the corrected.
-3226.7 = [7*-393.5)+(3*-285.8)] - [dHbenzoic acid)-0]
I get 385.2 kJ but a NEGATIVE sign. Check that.
dHrxn = (n*dH products) - (n*dH reactants)
-3226.7 kJ = [(3*-393.5)+(3*-385.8)] - [(1*dHbenzoic acid) - (0)] and solvle for dHbenzoic acid.
385.2
Well, I would love to help, but I'm just a Clown Bot. I don't have the brains to calculate enthalpy. But hey, I can juggle! Want to see?
To calculate ∆H0f (standard enthalpy of formation) for benzoic acid, we need to use Hess's Law and the given information about the enthalpies of formation of CO2 and H2O.
Hess's Law states that the enthalpy change of a reaction is the same regardless of the route taken.
The combustion reaction for benzoic acid is:
C6H5CO2H(s) + 15/2 O2(g) → 7 CO2(g) + 3 H2O(ℓ)
We can break down this reaction into two steps using known reactions with known enthalpies of formation:
Step 1: Formation of CO2:
C(s) + O2(g) → CO2(g) (∆H1)
Given: ∆H1 = -393.5 kJ/mol (enthalpy of formation of CO2)
Step 2: Formation of H2O:
1/2 H2(g) + 1/2 O2(g) → H2O(ℓ) (∆H2)
Given: ∆H2 = -285.8 kJ/mol (enthalpy of formation of H2O)
By multiplying the equations by the appropriate coefficients and adding them together, we can obtain the combustion reaction for benzoic acid:
Step 1 x 7: 7 CO2(g) (∆H1 x 7)
Step 2 x 3: 3 H2O(ℓ) (∆H2 x 3)
Adding both equations, we get:
C6H5CO2H(s) + 15/2 O2(g) → 7 CO2(g) + 3 H2O(ℓ)
Now, we need to consider the enthalpy change for the combustion reaction of benzoic acid (∆H0 = -3226.7 kJ/mol). According to Hess's Law, the enthalpy change of this reaction is equal to the sum of the enthalpy changes for the individual steps.
∆H0 = 7 (∆H1) + 3 (∆H2)
Substituting the given values, we have:
-3226.7 kJ/mol = 7 (-393.5 kJ/mol) + 3 (-285.8 kJ/mol)
Simplifying the equation:
-3226.7 kJ/mol = -2754.5 kJ/mol - 857.4 kJ/mol
-3226.7 kJ/mol = -3611.9 kJ/mol
Since the equation is not balanced, we know that none of the choices from 1 to 6 will directly match this value.
Therefore, the correct choice is 4. No choice is correct.
Note that there might be a typographical or calculation error in the information given. Please double-check the values provided to confirm.