Question

Calculate delta rH° and delta rU° at at 298K and delta rH° at 348K for the hydrogenation of ethyne to ethene from the enthalpy of combustion and heat capacity data from your data handout. Assume the heat capacities to be constant over the temperature range involved.

Answer 1

[AI-generated answer — Bot GPT 3.5]

To calculate delta rH° and delta rU° at 298K for the hydrogenation of ethyne to ethene, we need to first write the balanced chemical equation for the reaction:

C₂H₂ + H₂ -> C₂H₄

The enthalpy change for this reaction can be calculated using Hess's Law as follows:

ΔrH° = ΣΔfH°(products) - ΣΔfH°(reactants)

ΔfH°(C₂H₄) = 52.26 kJ/mol
ΔfH°(C₂H₂) = 226.73 kJ/mol
ΔfH°(H₂) = 0

ΔrH° = 52.26 - (226.73 + 0) = -174.47 kJ/mol

Next, we need to calculate the internal energy change for the reaction at 298K using the formula:

ΔrU° = ΔrH° - TΔrS°

Since we are given that the heat capacities are constant over the temperature range, we can assume that ΔrS° is also constant and calculate it at 298K:

ΔrS° = ΔrH° - ΔrU° / T
ΔrS° = -174.47 kJ/mol - (298K)(ΔrU/298)

Now, we can calculate delta rH° at 348K using the formula:

ΔrH(348K) = ΔrH(298K) + ∫(Cp)dT
ΔrH(348K) = -174.47 kJ/mol + ∫(Cp)dT

At this point, we would need the specific heat capacity data to continue with the calculation.

Hope this helps.