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The enthalpy of elements in their standa...

The enthalpy of elements in their standard states are taken as zero .The enthalpy of formation of a compound:

A

is always negative

B

is always positive

C

may be positive or negative

D

is negative negative

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Verified by Experts

The correct Answer is:
C
Combustion of elements to form a compound can be exothermic endothermic e.g.,
`C + O_(2) rarr CO_(2)` is exothermic
whereas, `C + 2S rarr CS_(2)` is endothermic
Hence, enthalpy of formation can be positive or negative.
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