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Given that the enthalpy change of water is -285.8kj/mol and tgat of carbon dioxide is -393.5kj/mol and that of nonane...is -6125.5kj/mol.. Calculate the standard enthalpy of formation of nonane applying hess' s law
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Hess's Law:
The standard enthalpy of formation of a compound is the enthalpy change when one mole of the compound is formed from its constituent elements in their standard states.
We can use Hess's Law to calculate the standard enthalpy of formation of nonane using the enthalpy changes of water, carbon dioxide, and nonane. Hess's Law states that the overall enthalpy change of a reaction is equal to the sum of the enthalpy changes of the individual steps in the reaction.
We can write the following equation for the formation of nonane from its constituent elements:
C9H20 (g) → 9C (s) + 10H2 (g)
The enthalpy change for this reaction is equal to the sum of the enthalpy changes for the following reactions:
C (s) + O2 (g) → CO2 (g) ΔH = -393.5 kJ/mol
2H2 (g) + O2 (g) → 2H2O (l) ΔH = -285.8 kJ/mol
9C (s) + 10H2O (l) → C9H20 (g) + 9O2 (g) ΔH = -6125.5 kJ/mol
We can add these equations together to get the overall equation for the formation of nonane from its constituent elements:
C9H20 (g) → 9CO2 (g) + 10H2O (l)
The enthalpy change for this reaction is equal to the sum of the enthalpy changes for the individual reactions, or -6125.5 kJ/mol + 9(-393.5 kJ/mol) + 10(-285.8 kJ/mol) = -411.0 kJ/mol.
Therefore, the standard enthalpy of formation of nonane is -411.0 kJ/mol.
The standard enthalpy of formation of a compound is the enthalpy change when one mole of the compound is formed from its constituent elements in their standard states.
We can use Hess's Law to calculate the standard enthalpy of formation of nonane using the enthalpy changes of water, carbon dioxide, and nonane. Hess's Law states that the overall enthalpy change of a reaction is equal to the sum of the enthalpy changes of the individual steps in the reaction.
We can write the following equation for the formation of nonane from its constituent elements:
C9H20 (g) → 9C (s) + 10H2 (g)
The enthalpy change for this reaction is equal to the sum of the enthalpy changes for the following reactions:
C (s) + O2 (g) → CO2 (g) ΔH = -393.5 kJ/mol
2H2 (g) + O2 (g) → 2H2O (l) ΔH = -285.8 kJ/mol
9C (s) + 10H2O (l) → C9H20 (g) + 9O2 (g) ΔH = -6125.5 kJ/mol
We can add these equations together to get the overall equation for the formation of nonane from its constituent elements:
C9H20 (g) → 9CO2 (g) + 10H2O (l)
The enthalpy change for this reaction is equal to the sum of the enthalpy changes for the individual reactions, or -6125.5 kJ/mol + 9(-393.5 kJ/mol) + 10(-285.8 kJ/mol) = -411.0 kJ/mol.
Therefore, the standard enthalpy of formation of nonane is -411.0 kJ/mol.
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