02-09-2011 Lecture

02-09-2011 Lecture - and bonds are made (releases energy)...

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Covalent Bonds – Bond Energies H C H H H Methane 1652 kJ mol -1 is required to break methane apart into its elements Chloromethane 1578 kJ mol-1 is required to break methane apart into its elements Cl C H H H C-H Bond Strength = 413 kJmol -1 C-Cl Bond Strength = 339 kJmol -1
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Bond Energies
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In a chemical reaction bonds are broken (requires energy) and bonds are made (releases energy) Bond energy values can be used to estimate the energies of a reaction: H 2 (g) + F 2 (g) 2HF (g) Bonds Broken: H-H, 432 kJmol -1 F-F, 154 kJmol -1 Bonds Made: H-F, 565 kJmol -1
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Δ H = Σ n×D (bonds broken) – Σ n×D (bonds formed) In a chemical reaction bonds are broken (requires energy)
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Unformatted text preview: and bonds are made (releases energy) Bond energy values can be used to estimate the energies of a reaction: H 2 (g) + F 2 (g) 2HF (g) Δ H = Negative Energetically Favorable Δ H = Positive Energetically Unfavorable Example Estimate the Δ H for the following reaction: + 2Cl 2 (g) CF 2 Cl 2 (g) CH 4 (g) 2F 2 (g) + 2HCl(g) 2HF(g) + + Example Estimate the Δ H for the following reaction: N N (g) + 3H 2(g) 2NH 3 (g) Example Estimate the Δ H for the following reaction: H 2 S(g) SF 4 (g) 3F 2 (g) + 2HF(g) + Your Turn Your Turn...
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This note was uploaded on 10/13/2011 for the course CHEM 101 taught by Professor Fitts during the Fall '08 term at UPenn.

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02-09-2011 Lecture - and bonds are made (releases energy)...

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