Chemistry - Thermochemistry Question with Solution | TestHub
When carbon is burnt in a definite amount of oxygen, the product will be CO if excess amount of carbon is present and the product will be CO2 if excess amount of O2 is present. The enthalpies of formation of CO(g) and CO2(g) are -26.4 and -95 kcal/mol, respectively. In which of the following case, the amount of heat evolved will be maximum?
Options:
Answer:
Solution:
(a) When O₂ is the limiting reactant, 4.5 mol of O₂ yields 9 mol of CO. The heat generated is 9 × 26.4 = 237.6 kcal.
(b) If 2 mol of C and 2 mol of O₂ react, they produce 2 mol of CO₂. The heat generated is 2 × 95 = 190 kcal.
(c) When 3.5 mol of O₂ burns 3.5 mol of C to form CO₂, the heat generated is 3.5 × 95 = 332.5 kcal.
(d) If 2.5 mol of C and 2.5 mol of O₂ react, they produce 2.5 mol of CO₂. The heat generated is 2.5 × 95 = 237.5 kcal.
The maximum heat generated occurs in case (c).
