Estimate the enthalpy change for the following reaction
OH(g)+CH4(g)==>CH3(g)+H2O(g)
To estimate the enthalpy change for the given reaction, we need to use Hess's law or consider the enthalpies of formation.
Hess's law states that the overall enthalpy change for a reaction is equal to the sum of the enthalpy changes of individual reactions that make up the overall reaction. In this case, we can break the given reaction into two steps:
Step 1: OH(g) + H2(g) → H2O(g)
Step 2: H2(g) + CH4(g) → CH3(g) + H2(g)
Now let's find the enthalpy changes for each step:
Step 1: OH(g) + H2(g) → H2O(g)
To find the enthalpy change for this reaction, you can refer to known enthalpies of formation. The enthalpy change for the formation of OH(g) and H2O(g) can be found from tables or reference books. Let's assume that the enthalpy change for the formation of OH(g) is X kJ/mol and the enthalpy change for the formation of H2O(g) is Y kJ/mol.
The enthalpy change for Step 1 will be Y - X kJ/mol.
Step 2: H2(g) + CH4(g) → CH3(g) + H2(g)
In this step, we can see that H2(g) appears on both sides of the equation and cancels out. So, the enthalpy change for this step will be zero since no new bonds are formed or broken.
Now, to find the overall enthalpy change for the given reaction, we sum up the enthalpy changes from each step:
Overall Enthalpy Change = Enthalpy Change (Step 1) + Enthalpy Change (Step 2)
Based on the information provided, the estimated enthalpy change for the given reaction can be calculated as:
Overall Enthalpy Change = (Y - X) kJ/mol + 0 kJ/mol = (Y - X) kJ/mol
Please note that the actual values of enthalpy changes for formation reactions might vary depending on the specific conditions and reference sources. To get a more accurate estimate, you can refer to reliable sources for the enthalpies of formation of OH(g) and H2O(g).