Calculate the standard enthalpy change of the reaction
ClO(g)+O3->ClO2(g)+O2(g)
Look up delta Ho in the standard tables and
delta Hrxn = (sum delta H products)-(sum delta H reactants)
To calculate the standard enthalpy change of a reaction, you need to know the standard enthalpies of formation of all the reactants and products involved in the reaction. The standard enthalpy of formation (ΔH°f) is the change in enthalpy that occurs when one mole of a compound is formed from its elements in their standard states at 298 K and 1 atm.
To calculate the standard enthalpy change of the reaction, you can use the following equation:
ΔH°rxn = ΣnΔH°f(products) - ΣmΔH°f(reactants)
Where:
ΔH°rxn = standard enthalpy change of the reaction
n, m = stoichiometric coefficients of products and reactants
ΔH°f(products) = standard enthalpy of formation of the product compound
ΔH°f(reactants) = standard enthalpy of formation of the reactant compound
Let's find the standard enthalpies of formation for the compounds involved in the reaction:
- ClO(g) does not have a standard enthalpy of formation. We'll assume it to be zero.
- O3(g) has a standard enthalpy of formation of 142.7 kJ/mol.
- ClO2(g) has a standard enthalpy of formation of -164.2 kJ/mol.
- O2(g) has a standard enthalpy of formation of 0 kJ/mol.
Substituting these values into the equation, we get:
ΔH°rxn = (1)(-164.2 kJ/mol) + (1)(0 kJ/mol) - (1)(142.7 kJ/mol) - (1)(0 kJ/mol)
= -306.9 kJ/mol
Therefore, the standard enthalpy change of the reaction ClO(g) + O3(g) -> ClO2(g) + O2(g) is -306.9 kJ/mol.
To calculate the standard enthalpy change of a reaction, you need to use Hess's law or standard enthalpy of formation data.
Hess's law states that the enthalpy change of a reaction is the same regardless of the path taken from reactants to products. To apply Hess's law, we break the given reaction into a series of simpler reactions with known enthalpy changes.
First, let's write down the balanced chemical equation for the given reaction:
ClO(g) + O3(g) -> ClO2(g) + O2(g)
Next, we need to find the individual enthalpy changes for each of the simpler reactions:
1. Cl2(g) + O3(g) -> Cl2O6(g) (formation of ClO2)
2. Cl2(g) -> 2 Cl(g) (bond dissociation of Cl2)
3. O3(g) -> 1.5 O2(g) (bond dissociation of O3)
4. Cl(g) + O2(g) -> ClO(g) (formation of ClO)
Now, we can look up the enthalpy changes of these reactions in a standard enthalpy of formation table or data source.
1. ΔH1 = ΔHf(ClO2)
2. ΔH2 = 2 × ΔHf(Cl) - ΔHf(Cl2)
3. ΔH3 = 1.5 × ΔHf(O2) - ΔHf(O3)
4. ΔH4 = ΔHf(ClO)
Finally, we calculate the standard enthalpy change of the overall reaction by summing the individual enthalpy changes:
ΔH = ΔH1 + ΔH2 + ΔH3 + ΔH4
Note: ΔHf represents the standard enthalpy of formation.
By looking up the standard enthalpy of formation values for the species involved and performing the calculations, you can determine the standard enthalpy change of the reaction.