This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Bond H (kJ/mole) Bond Length C=C 614 1.37 CC 839 1.20 C-N 305 1.43 C=N 615 1.38 CN 891 1.16 We can use these average bond enthalpy changes to calculate the approximate enthalpy change for reactions. For example, to calculate the change in enthalpy for the following reaction: H 2(g) + F 2(g) 2 HF (g) we identify and count all the bonds that are broken (shown in red) and formed (shown in blue). H H + F F 2 H F Substituting the average bond enthalpies: D H-H = 432 kJ/mole, D F-F = 154 kJ/mole, D H-F = 565 kJ/mole in the expression H = (H of bonds broken) - (H of bonds formed) we obtain H = [ (1 mole) (432 kJ/mole) + (1 mole) (154 kJ/mole) ]- [ (2 moles) (565 kJ/mole) ] = -544 kJ...
View Full Document
This note was uploaded on 07/31/2008 for the course CHY 152 taught by Professor Foucher during the Winter '08 term at Ryerson.
- Winter '08