Question

How I do find the delta h for the reaction

Answer 1

To find the delta H for a reaction, apply Hess's Law by writing the known reactions with their ΔH values and combine them to yield the target reaction, reversing reactions and changing signs of ΔH when necessary, and adjusting coefficients and ΔH values accordingly.

Step-by-step explanation:

To find the delta H (ΔH) for a reaction, you need to use Hess's Law, which tells us that the enthalpy change for an overall reaction is the sum of the enthalpy changes for the individual steps of the reaction. This is because enthalpy is a state function and only depends on the initial and final state of a process, not on the path taken between those states. To utilize Hess's Law, follow these steps:

1. Write the chemical equations for known reactions with ΔH values that, when combined, yield the desired reaction.
2. Reverse reactions if necessary, and in such cases, change the sign of ΔH.
3. If an equation's coefficients need to be adjusted, multiply ΔH by the same factor.
4. Add the ΔH values of the individual reactions to determine the ΔH for the overall reaction.

Remember that when you reverse a reaction or adjust the coefficients, make sure to change the ΔH accordingly. The physical states of reactants and products should also be considered as they affect the magnitude of ΔH.

Answer 2

ΔH = -276.6 kJ

Explanation

Given that:

N₂(g) + 3H₂(g) → 2NH₃(g); ΔH = -92.2 kJ

Then ΔH for the reaction 3N₂(g) + 9H₂(g) → 6NH₃(g) will be:

ΔH = 3 x -92.2 kJ = -276.6 kJ