The standard enthalpy change (ΔH°) for the given reaction is approximately -103.8 kJ/mol.
To calculate the standard enthalpy change (ΔH°) for the given reaction:
CH3OH + HBr → CH3Br + H2O
You can use the standard enthalpy of formation values for each compound involved in the reaction. The standard enthalpy of formation (ΔHf°) represents the change in enthalpy when one mole of a compound is formed from its elements in their standard states.
Here are the standard enthalpy of formation values:
- ΔHf° for CH3OH (methanol) = -238.6 kJ/mol
- ΔHf° for HBr (hydrogen bromide) = -36.4 kJ/mol
- ΔHf° for CH3Br (methyl bromide) = -93.0 kJ/mol
- ΔHf° for H2O (water) = -285.8 kJ/mol
Now, you can use these values to calculate ΔH° for the reaction:
ΔH° = ΣΔHf°(products) - ΣΔHf°(reactants)
ΔH° = [ΔHf°(CH3Br) + ΔHf°(H2O)] - [ΔHf°(CH3OH) + ΔHf°(HBr)]
ΔH° = [(-93.0 kJ/mol) + (-285.8 kJ/mol)] - [(-238.6 kJ/mol) + (-36.4 kJ/mol)]
Now, calculate the values:
ΔH° = [-378.8 kJ/mol] - [-275.0 kJ/mol]
ΔH° = -378.8 kJ/mol + 275.0 kJ/mol
ΔH° = -103.8 kJ/mol
So, the standard enthalpy change (ΔH°) for the given reaction is approximately -103.8 kJ/mol.