how do I find the ÄH for C2H4 + O3 --> CH3CHO + O2?
If you want it at 25o look up delta Hf for CH3CHO, O2, O3, and C2H4. Then
delta Hreaction = (delta Hproducts - delta Hreactants).
delta Hf for O2 will be zero
where would i look up the delta Hf for CH3CHO, O2, O3, and C2H4? online?
Be sure and read the prefix for the tables because they list different parts of the table in different units.
http://en.wikipedia.org/wiki/Standard_enthalpy_change_of_formation_(data_table)
To find the enthalpy change (ΔH) for the reaction C2H4 + O3 → CH3CHO + O2, you will need to use Hess's law or standard enthalpy of formation values.
Here's a step-by-step guide to finding ΔH using both methods:
Method 1: Using Hess's Law
1. Write the balanced chemical equation for the reaction:
C2H4 + O3 → CH3CHO + O2
2. Identify known reactions: Look for other reactions with known enthalpy changes (ΔH) that can be used to cancel out certain compounds from the given reaction.
3. Manipulate the known reactions: If needed, multiply or reverse the known reactions to match the stoichiometry of the given reaction.
4. Add the manipulated reactions: Add the known reactions together, ensuring that the compounds that appear on both sides of the equations cancel each other out.
5. Determine the overall enthalpy change: The sum of the enthalpy changes of the manipulated reactions will give you the ΔH for the given reaction.
Method 2: Using Standard Enthalpy of Formation (ΔHf) values
1. Determine the standard enthalpy of formation (ΔHf) values: Look up the ΔHf values for each compound involved in the reaction.
2. Calculate the ΔH for reactants: Multiply the ΔHf values of the reactants by their stoichiometric coefficients and sum them up.
3. Calculate the ΔH for products: Multiply the ΔHf values of the products by their stoichiometric coefficients and sum them up.
4. Determine the overall ΔH: Subtract the sum of the ΔH for the reactants from the sum of the ΔH for the products. Make sure to account for the sign of the ΔHf values.
Remember to use consistent units for the enthalpy values (usually kJ/mol), and ensure that the stoichiometry is correctly balanced in the chemical equation.
Note: If the ΔHf values are not given, you may need to use bond dissociation energies or look for alternative sources to obtain the needed values.
Using either of these methods should allow you to find the enthalpy change (ΔH) for the given reaction.