Chemical Thermodynamics Question 316

Question: Evaluate $ \Delta U $ at 500 K for the process $ Mg(s)+2HCl(g)\to MgCl_2(s)+H_2(g)\Delta H=-109 $ kcal The volume change of solids to be ignored

Options:

A) -204 kcal

B) -108 kcal

C) -9 kcal

D) +9 kcal

Show Answer

Answer:

Correct Answer: B

Solution:

  • $ \Delta H=\Delta U+\Delta n_{g}RT $

$ -109=\Delta U+( \frac{-1\times 2\times 500}{1000} )kcal $

$ -109=\Delta U-1,kcal $

$ \Delta U=-109+1=-108,kcal $



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