Chemical Thermodynamics Question 224

Question: Values of heats of formation for $ SiO_2 $ and $ MgO $ are $ -48.4 $ and $ -34.7,kJ $ respectively. The heat of the reaction $ 2Mg+SiO_2\to 2MgO+Si $ is [KCET 1990]

Options:

A) $ 21.16,kJ $

B) $ -21.10,kJ $

C) $ -13.62,kJ $

D) $ 13.6,kJ $

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Answer:

Correct Answer: B

Solution:

$ \Delta {H_{(reaction)}}=2\Delta H_{f}^{0},(MgO)=-\Delta H_{f}^{0},(SiO_2) $

$ =2,(-,34.7)-(-,48.4)=-21,kJ. $



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