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Section 4 d. Breaking and making bonds. Bond energies. The table below shows the amount of energy needed to break the bond and the amount of energy released when that bond is made. s ample calculation. CH 4 ( g ) + 2O 2 ( g ) CO 2 ( g ) + 2H 2 O ( g ) - PowerPoint PPT Presentation
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Section 4 d
Breaking and making bonds
Bond energies• The table below shows the amount of energy needed
to break the bond and the amount of energy released when that bond is made
bond bond energy kJ/mol
bond bond energy kJ/mol
H - H 436 H – Cl 432C - H 413 N - H 391O - H 464 O = O 498C = O 746 N N 945Cl - Cl 243 Br - Br 190C – C 348 H - Br 366C = C 612
sample calculation
CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (g)
ΔH = bonds broken – bonds made = 2640 – 3338 = - 700 kJ
reactants products CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (g)
bonds broken bonds made(4 (C-H) + 2 (O=O)) (2 (C=O) + 4 (H-O))
(4 x 413) + ( 2 x 498) (2 x 746) + ( 4 x 464)
= 2648 kJ = 3338 kJ
Energy level diagram - exothermic
• The energy level diagram below includes the energy taken into break bonds and the energy released when making new ones
Same energy level diagram
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