Question

Carbon monoxide (CO) is burnt in presence of 200% excess pure oxygen and the flame temperature achieved is 2298 K. The inlet streams are at 25°C. The standard heat of formation (at 25°C) of CO and CO2 are −110 kJ mol⁻¹ and −390 kJ mol⁻¹, respectively. The heat capacities (in J mol⁻¹ K⁻¹) of the components are Cp,O2=25+14×10⁻³T, Cp,CO2=25+42×10⁻³T, where T is the temperature in K. The heat loss (in kJ) per mole of CO burnt is _____

Accepted Answer

The correct answer is 35 kJ (± 3). Basis 1 mol CO burnt: CO+0.5O2→CO2, ΔHrxn(298K)=−390−(−110)=−280 kJ. Stoichiometric O2=0.5 mol; with 200% excess, O2 fed=1.5 mol, O2 remaining=1.0 mol. Sensible heat to raise products from 298K to 2298K (ΔT=2000K): CO2 (1 mol): ∫(25+0.042T)dT=25(2000)+0.021(2298²−298²)=50,000+109,032=159,032 J. O2 (1 mol): ∫(25+0.014T)dT=50,000+0.007(5,192,000)=50,000+36,344=86,344 J. Total sensible heat=245,376 J≈245.4 kJ. Heat loss=heat released−sensible heat absorbed=280−245.4≈34.6 kJ per mole CO burnt.

Explanation