Chemistry
Chemistry
Problem
Nitrogen trichloride can be prepared directly from its elements according to the following gas-phase reaction at 298 K: N₂(g) + 3 Cl₂(g) → 2 NCl₃(g) In a laboratory experiment, 0.0250 mol of N₂ reacted completely with excess Cl₂, absorbing 5.80 kJ of heat from the surroundings. Average bond energies (kJ mol⁻¹): N≡N 941 Cl—Cl 243 N—Cl ? (a) Using the experimental data, determine ΔH°rxn (in kJ mol⁻¹ of reaction as written) for the synthesis of NCl₃. (b) Identify the total number of each bond type broken and formed per mole of reaction. (c) Using results from parts (a) and (b), calculate the average bond energy of the N—Cl bond, B(N—Cl), in kJ mol⁻¹. (d) Compare your calculated B(N—Cl) to the average Cl—Cl bond energy provided. Using bonding concepts, explain why the two values are similar or different.Intuitive explanation
This is a bond energy problem where you're using the heat absorbed to work backward and find an unknown bond strength. The key insight is that the heat change for a reaction equals the energy required to break all reactant bonds minus the energy released when product bonds form—rearrange this relationship to solve for the missing N—Cl bond energy. Since you know the moles of reaction that occurred and the total heat absorbed, you can find the enthalpy change per mole, then use the bond energy equation to isolate the unknown.
Intuitive explanation
This is a bond energy problem where you're using the heat absorbed to work backward and find an unknown bond strength. The key insight is that the heat change for a reaction equals the energy required to break all reactant bonds minus the energy released when product bonds form—rearrange this relationship to solve for the missing N—Cl bond energy. Since you know the moles of reaction that occurred and the total heat absorbed, you can find the enthalpy change per mole, then use the bond energy equation to isolate the unknown.