Chemical Thermodynamics Question 319
Question: The standard heat of formation of $ U_3O_8 $ is -853.5 kcal/mol and the standard heat of the reaction $ 3UO_2+O_2\to U_3O_8 $ is -76.01 kcal. The standard heat of formation of $ UO_2 $ is
Options:
A) -1083 kJ $ mo{{l}^{-1}} $
B) -108.3 kJ $ mo{{l}^{-1}} $
C) -10.83 kJ $ mo{{l}^{-1}} $
D) -1.083 kJ $ mo{{l}^{-1}} $
Show Answer
Answer:
Correct Answer: B
Solution:
- $ 3UO_2+O_2\to U_3O_8 $
$ \Delta H{}^\circ =\Delta H_{f}^{\circ }(U_3O_8)-\Delta H_{f}^{\circ }(O_2)-3\Delta H_{f}^{\circ }(UO_2) $
$ \Rightarrow 3\Delta H_{f}^{\circ }(UO_2)=-\Delta H_{f}^{\circ }+\Delta H_{f}^{\circ }(U_3O_8)-\Delta H_{f}^{\circ }(O_2) $ or $ \Delta H_{f}^{\circ }(UO_2)=\frac{-(-76.0)+(-853.5)-0}{3} =-108.3 kJ $
