Consider the reactions below:

() + 2 (g) (g) + 3 () . . = 1250 kJ (1)

2 () + 4 (g) 2(g) + 6 () (2)

() + 2 (g) (g) + 3 () (3)

From the chemical equations given above,

i. Referring to chemical equation (1), state whether the equation is exothermic or endothermic.

(1 mark)

ii. Based on your answer in (i) above, explain the heat of reaction in terms of energy associated with breaking and forming of molecular bonds.

(3 marks)

iii. Briefly explain how would heat of reaction values for reaction (2) and for reaction (3) differ from the one given for reaction (1).

(3 marks)

a

bb. In a commercial process, a company is planning to burn methane (CH₄) with excess air in an adiabatic reactor. The adiabatic reactor is insulated with lightweight refractory concretes material that able to withstand temperatures at range between 390 to 510C. The combustion equation is stated as follows:

CH₄ (g) + 2O₂ (g) CO₂ (g) + 2H₂O (g)

As a process engineer, you are required to determine the percentage of excess air required for combustion of 300 mol/hr of methane. The methane and excess air are fed at 25C and 1 atm. The percentage conversion of methane is 60%. Decide one (1) final adiabatic temperature within the range of temperature which insulated material can withstand in your calculation.