Broken Bonds Quick Check | Unit 2 Lesson 4

Use the reaction and bond information to answer the question. H₂ + CO₂ → CH₂O₂ Reactant bond energies: H—H is 432 kJ/mol, C=O is 799 kJ/mol Product bond energies: C—H is 413 kJ/mol, C=O is 745 kJ/mol, C—O is 358 kJ/mol, O—H is 467 kJ/mol How much energy must this system absorb before the reaction can begin?

2,030 kJ

Use the chemical equation and the bond diagram to answer the question. H₂ + O₂ → H₂O₂ H—H + O=O → H—O—O—H The energy of the H—H bond is 432 kJ/mol. The energy of the O=O bond is 495 kJ/mol. The energy of the O—H bond is 467 kJ/mol. The energy of the O—O bond is 146 kJ/mol. Which bond is the strongest?

O=O

Use the reaction and bond information to answer the question. C₂H₆ → C₂H₄ + H₂ Reactant bond energies: H—C = 413 kJ/mol, C—C single bond = 347 kJ/mol Product bond energies: H—C = 413 kJ/mol, C=C double bond = 614 kJ/mol, H-H = 432 kJ/mol Based on the bond energies, is this reaction endothermic or exothermic? Why or why not?

The reaction is endothermic, because stronger bonds are broken than formed.

Use the reaction and bond information to answer the question. C₂H₂ + 3H₂ → 2CH₄ Reactant bond energies: H—C = 413 kJ/mol, C—C triple bond = 839 kJ/mol, H-H = 432 kJ/mol Product bond energies: H-C = 413 kJ/mol Based on the bond energies, would this reaction occur without the addition of energy? Why or why not?

Yes, it would occur without additional energy because the reaction is exothermic.

In order to break a bond, energy must be

absorbed.