Question

Use the equation and bond energies to answer the question.
2H₂O ⇒ 2H₂ + O2

H-O: 467 kJ/mol
H-H: 432 kJ/mol
O=O: 495 kJ mol

What is the total energy of the reaction? Is this an endothermic or exothermic reaction?

A. -509 kJ/mol, endothermic
B. 509 kJ/mol, endothermic
C. -509 kJ/mol, exothermic
D. 509 kJ/mol, exothermic
(Energy in Chemical Reaction Unit I test)

Answer 1

Answer:

B

Explanation:

• Bond enthalpy of rxn= Bond entahlpy of reacant - bond enthalpy of product
• =2{2(O-H)} - [2(H-H) + (O-O].
• =4(467)-[2(432) +495]
• =1868-1359
• =509KJ/mol
• ∆H=+,endothermic Rxn