Chemistry - Thermochemistry Question with Solution | TestHub
When 1.2 g graphite is burnt in limited supply of oxygen at 298 K and 1 bar, 2.64 kcal heat is released. No solid is left and the gaseous product formed is not absorbed in aqueous KOH solution. When 1.2 g graphite is burnt in excess supply of oxygen at 298 K and 1 bar, 9.4 kcal heat is released. No solid residue is left and the gaseous product formed is absorbed completely in aqueous KOH solution. When 4.4 g CO2(g) is decomposed completely into CO(g) and O2(g) at 298 K and 1 bar, the enthalpy of system increases (in kcal) by
Answer:
Solution:
Product not absorbed in KOH is CO: C + 1/2O2 → CO, ΔH = -2.64 × 12/1.2 = -26.4 kcal/mol. Absorbed product is CO2: C + O2 → CO2, ΔH = -9.4 × 12/1.2 = -94 kcal/mol. Then CO2 → CO + 1/2O2 has ΔH = +94 - 26.4 = +67.6 kcal/mol. For 4.4 g CO2 = 0.10 mol: ΔH = 67.6 × 0.10 = 6.76 ≈ 7 kcal. Answer: 7.
