Chemistry
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ISBN: 9781305957404
Author: Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
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![### Calculation of Reaction Enthalpy using Hess's Law
To calculate the ΔH for the reaction:
\[ \text{N}_2\text{H}_4 + 2 \text{H}_2\text{O}_2 \rightarrow \text{N}_2 + 4 \text{H}_2\text{O} \]
We will use Hess's Law and the following given data:
1. \(\text{N}_2\text{H}_4 + \text{O}_2 \rightarrow \text{N}_2 + 2 \text{H}_2\text{O}, \, \Delta H = -622.2 \, \text{kJ}\)
2. \(\text{H}_2 + \frac{1}{2} \text{O}_2 \rightarrow \text{H}_2\text{O}, \, \Delta H = -285.8 \, \text{kJ}\)
3. \(\text{H}_2 + \text{O}_2 \rightarrow \text{H}_2\text{O}_2, \, \Delta H = -187.8 \, \text{kJ}\)
### Steps for Calculation
Use the given enthalpies to arrange and manipulate equations to derive the target reaction. Follow Hess's Law by making sure equations add up correctly to give the desired overall reaction and sum their ΔH accordingly.
### Additional Note
Switching or reversing any of these reactions will require you to change the sign of the respective ΔH value. Ensure stoichiometric coefficients are balanced for accurate ΔH computation.
### Conclusion
Once calculations are complete, input the final ΔH value to determine the enthalpy change for the overall reaction.](https://content.bartleby.com/qna-images/question/394d8541-a3b5-4cf5-865d-319b45552e6b/b8890ef0-10f0-4aed-928a-a0c3189663a2/qaycl6dc_processed.jpeg)
Transcribed Image Text:### Calculation of Reaction Enthalpy using Hess's Law
To calculate the ΔH for the reaction:
\[ \text{N}_2\text{H}_4 + 2 \text{H}_2\text{O}_2 \rightarrow \text{N}_2 + 4 \text{H}_2\text{O} \]
We will use Hess's Law and the following given data:
1. \(\text{N}_2\text{H}_4 + \text{O}_2 \rightarrow \text{N}_2 + 2 \text{H}_2\text{O}, \, \Delta H = -622.2 \, \text{kJ}\)
2. \(\text{H}_2 + \frac{1}{2} \text{O}_2 \rightarrow \text{H}_2\text{O}, \, \Delta H = -285.8 \, \text{kJ}\)
3. \(\text{H}_2 + \text{O}_2 \rightarrow \text{H}_2\text{O}_2, \, \Delta H = -187.8 \, \text{kJ}\)
### Steps for Calculation
Use the given enthalpies to arrange and manipulate equations to derive the target reaction. Follow Hess's Law by making sure equations add up correctly to give the desired overall reaction and sum their ΔH accordingly.
### Additional Note
Switching or reversing any of these reactions will require you to change the sign of the respective ΔH value. Ensure stoichiometric coefficients are balanced for accurate ΔH computation.
### Conclusion
Once calculations are complete, input the final ΔH value to determine the enthalpy change for the overall reaction.
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