The value of ΔH° for the following reaction is -72 kJ. How many kJ of heat will be evolved when 1.0 mole HBr is formed in this reaction? H2(g) + Br2(g) → 2HBr(g)

1 Answer
Al E.
May 5, 2018

Consider,

#H_2(g) + Br_2(g) to 2HBr(g)#, where #DeltaH_"rxn"^° approx -72"kJ"#

Notice, two moles of the reactant are formed in the preceding data. The question states only one mole, thus we want to divide the equation (and thus the standard enthalpy of the reaction) by #2#.

Hence,

#(-72"kJ")/(2"mol") approx (-36"kJ")/"mol"#

is the molar standard enthalpy of this reaction.

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