The heat of formation is the change in enthalpy accompanying the formation of a substance from its elements at 298 K and 1 atm pressure. Since the enthalpies of elements are taken to be zero, the heat of formation \[(\Delta H)\] of compounds [NCERT 1978; KCET 1993]

The heat of formation is the change in enthalpy accompanying the forma

1.	The heat of formation is the change in enthalpy accompanying the formation of a substance from its elements at 298 K and 1 atm pressure. Since the enthalpies of elements are taken to be zero, the heat of formation \[(\Delta H)\] of compounds [NCERT 1978; KCET 1993]
A.	Is always negative
B.	Is always positive
C.	May be negative or positive
D.	Is zero
Answer» D. Is zero

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The heat of formation is the change in enthalpy accompanying the formation of a substance from its elements at 298 K and 1 atm pressure. Since the enthalpies of elements are taken to be zero, the heat of formation \[(\Delta H)\] of compounds [NCERT 1978; KCET 1993]

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