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# The standard enthalpy of formation of $\;NH_{3}\;$ is -46.0 kJ/mol . If the enthalpy of formation $\;H_{2}\;$ from its atoms is -436 kJ/mol and that of $\;N_{2}\;$ is -712 kJ/mol , the average bond enthalpy of N-H bond in $\;NH_{3}\;$ is :

$(a)\;-1102\;kJ/mol \qquad(b)\;-964\;kJ/mol\qquad(c)\;+352\;kJ/mol\qquad(d)\;+1056\;kJ/mol$