Answer: 2.06 × 10 ³ kJ = 2,060 kJ
Explanation:
1) Balanced chemical equation (given)
4NH₃ (g) + 5O₂ (g) → 4NO (g) + 6H₂O (g), δH rxn = − 906 kJ
2) Calculate the number of NH₃ moles in 155 g
i) molar mass of NH₃ = 14.007 g/mol + 3×1.008 g/mol = 17.031 g/mol
ii) number of moles = mass in grams / molar mass = 155 g / 17.031 g/mol = 9.10 mol of NH₃
3) Caculate the energy using proportions with the mole /energy ratio from the balanced chemical equation:
4 moles NH₃ / (-906 kJ) = 9.10 mol NH₃/ x
⇒ x = 9.10 mol NH₃ × (-906 kJ) / 4 mol NH₃ = - 2,061.15
Which rounded to three significan figures is 2.06 × 10 ³ kJ = 2,060 kJ