covalent bonding bond lengths bond energies. not all chemical bonds have the same strength vary...
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Covalent Bonding Bond LengthsBond Energies
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Not all chemical bonds have the same strength vary based on atom combination and the
amount of shared electrons between atoms
**More electrons in a chemical bond, atoms held more tightly**
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Bond Length Deals with covalent bonds only
Distance between nuclei of 2 atoms in a chemical bond
Dependent on atom type and bond order
bond # (double, triple, etc.), bond length
= Σ covalent radii of 2 atoms
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Example 1: Estimate the bond length of the nitrogen-
nitrogen bond in N2H4
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Example 2: Estimate the bond length for BrCl
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Bond Energy Chemical bonds constantly breaking/forming
Breaking bond—energy absorption
Bond formation—energy release
Bond Dissociation Energy (kJ/mol) Amount of energy needed to break ONE mole
of covalent bonds existing between 2 atoms
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How are bond energy and bond order related to each
other? Increase bond order, increase bond dissociation
energy
Neighboring atoms close to bond can influence dissociation energy
SOOOOOOO
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Bond Energy (cont.) Average Bond Energy
Average dissociation energies for molecules with a specific bond
ΔH = ΔH (bonds broken) - ΔH (bonds formed)
BUT ! ! !
ΔH ≈ Σ (BE) reactants - Σ (BE) products
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Example 1: Calculate the enthalpy of formation for
hydrazine (N2H4) using bond energies.
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Example 2: Using the following equation:
C2H6 + Cl2 C2H5Cl + HCl
Calculate the ΔH rxn.