Standard heat of formation is not zero for.. a) Na b) Cl2 c) Hg d) Br2 Please explain.?

1 Answer
anor277
Aug 1, 2018

I think you need to recheck the source of this question.

Explanation:

THe #"standard heat"# or #"standard enthalpy of formation"# is the enthalpy associated with ONE mole of substance from its constituent elements under standard conditions...the PHASES of each species must be specified if we are to approach this meaningfully...

For instance the standard enthalpy of formation of methane gas is the enthalpy associated with the reaction...

#C(s) + 2H_2(g) rarr CH_4(g) + Delta#

#Delta_"rxn"="standard enthalpy of formation of methane"#

This is approached experimentally, given that the #"standard enthalpy of formation"# of ELEMENTS in their standard states is defined to be ZERO. You need to work on the question and reproduce it faithfully.

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