Question

consider the following reaction at 25 °c:3 nio(s) 2 nh₃(g) → 3 ni(s) n₂(g) 3 h₂o(g)given the information in the table, calculate ∆h° for the reaction.

Answer 1

To calculate the enthalpy change for the reaction given, we must use Hess's law and the reaction data for ammonia formation, adjusting and reversing it to fit the reaction in question. The approximate enthalpy change calculation results in a 138.6 kJ/mol energy release.

Step-by-step explanation:

To calculate the standard enthalpy change (ΔH°) for the reaction 3NiO(s) + 2NH3(g) → 3Ni(s) + N2(g) + 3H2O(g) at 25 °C, we must use the standard enthalpy of formation values for the reactants and products involved.

The given reaction for the formation of ammonia:
N2(g) + 3H2(g) = 2NH3(g)
has an enthalpy change (ΔH) of −92.4 kJ/mol.

To find the ΔH° for our reaction, we will reverse the given reaction, doubling it, and then subtract it from the ΔH° value of the nitrogen and hydrogen reaction. The calculation is:

• Reverse the ammonia formation equation and multiply by 1.5 to match the amount of NH3 in our target reaction.
• Calculate the ΔH° for the new reaction using the fact that reversing a reaction changes the sign of ΔH°.
• Subtract the revised ΔH° from our reaction equation to find the desired enthalpy change for the targeted reaction.

In this case, the enthalpy changes are as follows:

• Reverse the ammonia formation: (1.5 × 2)NH3(g) → (1.5)N2(g) + (1.5 × 3)H2(g)
  The enthalpy change for this is 1.5 × 92.4 kJ/mol = 138.6 kJ/mol.
• The total ΔH° for our target reaction, therefore, becomes -138.6 kJ/mol (since the reversed reaction has its enthalpy change sign inverted).

Note that in this response, specific values of enthalpies of formation for the compounds NiO, Ni, and H2O were not provided. These would typically be required to perform an accurate Hess's law calculation. Since they are absent, we have approximated the calculation based on the reaction provided.