Reposted:
Use Hess's law to calculate the enthalpy change for the reaction:
3C(s) + 3H2(g) yield C3H6(g)
Given the following thermochemical equations:
2C3H6(g) + 9O2(g) yield 6CO2(g) + 6H2O(l) enthalpy change= -4116.0 kJ/mol
C(s) + O2(g) yield CO2(g) enthalpy change= -393.51 kJ/mol
H2(g) + 1/2O2(g) yield H2O(l) enthalpy change= -285.83 kJ/mol
never mind, i already figured it out :)
To use Hess's law to calculate the enthalpy change for the given reaction, we need to manipulate and combine the provided thermochemical equations to obtain the target reaction.
First, let's flip and multiply the first equation by 3 to balance the number of carbon atoms in the reactants and products:
3C3H6(g) + 27O2(g) yield 18CO2(g) + 18H2O(l) enthalpy change = -12,348.0 kJ/mol
Next, let's multiply the second equation by 3 and the third equation by 1:
3C(s) + 3O2(g) yield 3CO2(g) enthalpy change = -1180.53 kJ/mol
3H2(g) + 3/2O2(g) yield 3H2O(l) enthalpy change = -857.49 kJ/mol
Now, let's add the three manipulated equations together to get the target equation:
3C(s) + 3H2(g) + 3/2O2(g) yield C3H6(g) + 3CO2(g) + 3H2O(l)
After canceling out the terms that appear on both sides of the equation, we are left with:
3C(s) + 3H2(g) yield C3H6(g) + 3CO2(g) + 3H2O(l)
Now, let's calculate the net enthalpy change for the target equation using Hess's law. This can be done by summing up the enthalpy changes of the manipulated equations. Since enthalpy is a state function, the sum of enthalpy changes will give us the enthalpy change for the target equation.
ΔH = (-12,348.0 kJ/mol) + (-1180.53 kJ/mol) + (-857.49 kJ/mol)
= -14,385.02 kJ/mol
Therefore, the enthalpy change for the given reaction is -14,385.02 kJ/mol.