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

Options

A. is always negative
B. is always positive
C. May be positive or negative
D. Is never negative

Answer

C

Explanation

Reaction of elements to form a compound can be exothermic or 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