Question 23 please **Question 23**The enthalpy of reaction for the combustion of C to CO₂ is -393.5 kJ/mol C, and the enthalpy for the combustion of CO to CO₂ is -283.0 kJ/mol CO.(i) \( \text{C(s) + O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} \quad \Delta H = -393.5 \, \text{kJ} \)(ii) \( 2\text{CO(g)} + \text{O}_2\text{(g)} \rightarrow 2\text{CO}_2\text{(g)} \quad \Delta H = -283.0 \, \text{kJ} \)Using these data, calculate the enthalpy for the combustion of C to CO:(iii) \( 2\text{C(s)} + \text{O}_2\text{(g)} \rightarrow 2\text{CO(g)} \quad \Delta H = ? \)- A. -787.0 kJ- B. -504.0 kJ- C. 1070 kJ- D. None of the above

The reactions given are, 1) C (s) + O2 (g) ------> CO2 (g) ΔH = -393.5 KJ 2) 2 CO (g) + O2 (g) ------> 2 CO2 (g) ΔH = -283.0 KJ Since we need 2 C in the reactant side in the final reaction (iii). Hence multiplying reaction (1) with 2 to get (on multiplying any reaction with a constant, the ΔH of the reaction also gets multiplied by same constant as per the Hess's law), 3) 2 C (s) + 2 O2 (g) ------> 2 CO2 (g) ΔH = -393.5 X 2 = -787.0 KJ Now subtracting reaction 2 from 3 to eliminate CO2 from the reactions and get the final reaction as (on subtracting reactions, the ΔH of reaction also gets subtracted), => 2 C (s) + O2 (g) ------> 2 CO (g) ΔH = -787.0 - (-283.0) = -504.0 KJ Hence the answer is option B. -504.0 KJ.