The value of the equilibrium constant Kc for the reaction N2(g) +...

Question

The value of the equilibrium constant Kc for the reaction N2(g) + 3 H2(g) ⇌ 2 NH3(g) changes in the following manner as a function of temperature: Temperature (°C) Kc 300 9.6 400 0.50 500 0.058. (b) Use the standard enthalpies of formation given in Appendix C to determine the ΔH for this reaction at standard conditions. Does this value agree with your prediction from part (a)?

Accepted Answer

Step 1: Write the balanced chemical equation for the reaction: $ N_2(g) + 3 H_2(g) \rightleftharpoons 2 NH_3(g) $.. Step 2: Use the standard enthalpies of formation ($ \Delta H_f^\circ $) from Appendix C to calculate the $ \Delta H^\circ $ for the reaction. The formula is: $ \Delta H^\circ = \sum \Delta H_f^\circ (\text{products}) - \sum \Delta H_f^\circ (\text{reactants}) $.. Step 3: Substitute the standard enthalpies of formation for $ NH_3(g) $, $ N_2(g) $, and $ H_2(g) $ into the equation. Remember that the $ \Delta H_f^\circ $ for elements in their standard state, like $ N_2(g) $ and $ H_2(g) $, is zero.. Step 4: Calculate the $ \Delta H^\circ $ for the reaction using the values from Step 3. This will give you the enthalpy change for the reaction under standard conditions.. Step 5: Compare the calculated $ \Delta H^\circ $ with your prediction from part (a) regarding the temperature dependence of $ K_c $. If $ K_c $ decreases with increasing temperature, the reaction is exothermic, and the calculated $ \Delta H^\circ $ should be negative.