Question

Calculate the heat of reaction in (kJ) for the following reaction:

2CO(g) + O2(g) --> 2CO2(g)

given the following data:

C + 1/2O2 --> CO(g) delta H= -110.5 KJ/mol

C + O2(g) --> CO2(g) delta H= -393.5 KJ/ mol

Answer 1

Reaction 1 : C (s) + 1/2 O₂ (g) CO (g) : H₁ = -110.5 kJ/mol

Reaction 2 : C (s) + O₂ (g) CO₂ (g) : H₂ = -393.5 kJ/mol

Desired reaction : 2 CO (g) + O₂ (g) 2 CO₂ (g)

Step 1 : Reverse Reaction 1

Reaction 3 : CO (g) C (s) + 1/2 O₂ (g)

H₃ = -(H₁)

H₃ = -(-110.5 kJ/mol)

H₃ = 110.5 kJ/mol

Step 2 : Add Reaction 2 and Reaction 3

Reaction 4 : CO (g) + 1/2 O₂ (g) CO₂ (g)

H₄ = (H₂) + (H₃)

H₄ = (-393.5 kJ/mol) + (110.5 kJ/mol)

H₄ = -283.0 kJ/mol

Step 3 : Multiply Reaction 4 by a factor of 2

Reaction 5 : 2 CO (g) + O₂ (g) 2 CO₂ (g)

This is the desired reaction

H₅ = 2 * (H₄)

H₅ = 2 * (-283.0 kJ/mol)

H₅ = -566.0 kJ/mol

Heat of reaction is -566.0 kJ