The value of (∆H−∆U) for the formation of carbon monoxide (CO) from its elements at 298 K is: (R = 8.314 J K⁻¹ mol⁻¹)
Correct answer: A. 1238.78 J mol−1
- A. 1238.78 J mol−1
- B. −2477.57 J mol−1
- C. 2477.57 J mol−1
- D. −1238.78 J mol−1
Explanation
The reaction is C(s) + ½O₂(g) → CO(g). The relationship is ΔH - ΔU = ΔngRT. The change in moles of gas is Δng = (moles of gas products) - (moles of gas reactants) = 1 - 1/2 = +1/2. So, ΔH - ΔU = (+1/2)(8.314)(298) ≈ +1238.78 J/mol.
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About Internal Energy
Internal energy is the total microscopic kinetic and potential energy of a system and is a state function. The first law, ΔU = q + w, connects changes in internal energy with heat and work, including sign conventions, expansion or compression and constant-volume processes.
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