A) \[-3.8\]
B) \[-1.9\]
C) \[+3.8\]
D) \[+1.9\]
Correct Answer: D
Solution :
Key Idea: Use Hess law which states that total heat changes during a chemical reaction are independent of path. \[{{C}_{(diamond)}}+{{O}_{2}}\xrightarrow{{}}C{{O}_{2}}\] \[\Delta H=-395.4\text{ }kJ/mol\] ...(1) \[{{C}_{(graphite)}}+{{O}_{2}}\xrightarrow{{}}C{{O}_{2}}\] \[\Delta H=-393.5\text{ }kJ/mol\] ...(2) \[{{C}_{(graphite)}}\xrightarrow{{}}{{C}_{(diamond)}}\Delta H=?\] Subtracting Eq. (1) from Eq. (2) we get \[{{C}_{(graphite)}}\xrightarrow{{}}{{C}_{(diamond)}},\Delta H=1.9\,kJ/mol\]
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