How do you measure the enthalpy of formation of carbon monoxide?

1.	How do you measure the enthalpy of formation of carbon monoxide?
Answer» 1. Hess’s law can be applied to calculate the enthalpy of formation of carbon monoxide. It is very difficult to control the oxidation of graphite to give pure CO. However, enthalpy for the oxidation of graphite to CO₂ can be easily measured and enthalpy of oxidation of CO to CO₂ is also measurable. 2. The application of Hess’s law enables us to estimate the enthalpy of formation of CO. C + O₂ → CO₂∆H° = 393.5 kJ ….. (1) CO + 1/2 O₂ → CO₂ ∆H° = -283 kJ ….. (2) On inverting equation (2), we get CO₂ → CO + 1/2 O₂ ∆H° = + 283 kJ …… (3) On adding equations (2) and (3), we get C + 1/2 O₂ → CO ∆H° = 393 5 + 283 = 110.5kJ

Answer»

1. Hess’s law can be applied to calculate the enthalpy of formation of carbon monoxide. It is very difficult to control the oxidation of graphite to give pure CO.

However, enthalpy for the oxidation of graphite to CO₂ can be easily measured and enthalpy of oxidation of CO to CO₂ is also measurable.

2. The application of Hess’s law enables us to estimate the enthalpy of formation of CO.

C + O₂ → CO₂∆H° = 393.5 kJ ….. (1)

CO + 1/2 O₂ → CO₂ ∆H° = -283 kJ ….. (2)

On inverting equation (2), we get

CO₂ → CO + 1/2 O₂ ∆H° = + 283 kJ …… (3)

On adding equations (2) and (3), we get

C + 1/2 O₂ → CO ∆H° = 393 5 + 283 = 110.5kJ

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