Chemical bonding Flashcards
What is H-H bond enthalpy in H2 ?
435.8 kJ mol-1
What is the concept of resonance?
Whenever a single Lewis structure cannot describe a molecule accurately, a no. of structures with similar energy, positions of nuclei, bonding and non bonding pairs of electrons are taken as canonical structures of the hybrid which describes the molecule accurately.
What is N(triple bond)N in N2?
946.0 kJ mol-1
What is the bond dissociation enthalpy for HCl?
431.0 kJ mol-1
What is bond order?
Number of bonds between the two atoms in a molecule.
What is average bond enthalpy?
Total bond dissociation enthalpy upon number of bonds broken.
Which molecules and ions have identical bond orders?
Isoelectronic.
What will increase if we increase the bond order?
Bond enthalpy
How is resonance represented?
By double headed arrow.
What are the features of Resonance?
- Resonance stabilizes the molecule as the energy of the resonance hybrid is less than the energy of any single canonical structure.
- Resonance averages the bond characteristics as a whole.
What is non polar covalent bond?
When covalent bond is formed between two similar atoms, the shared pair of electron is equally attracted by two atoms. As a result electron pair is situated exactly between the two identical nuclei. This bond is called non polar covalent bond.
What is dipole moment?
Product of the magnitude of the charge and the distance between the centers of positive and negative charge.
In which unit is dipole moment expressed?
Debye units.
What is the value of 1 Debye?
1Debye = 3.33564 x 10^-30 C m
What decreases with increase in bond order?
Bond length
What is mathematical meaning of dipole moment?
Product of charge and distance of separation.
What is the net dipole moment of two O-H bonds in H2O?
1.85D = 6.17 x 10^-30 C m
What is the molecule (AB) HF:
a) Dipole moment?
b) Geometry?
a) 1.78 D
b) linear
What is molecule( AB )HCl :
a) Dipole moment?
b) Geometry?
a) 1.07 D
b) linear
What is molecule(AB) HBr:
a) Dipole moment?
b) Geometry?
a) 0.79 D
b) linear
What is molecule (AB) HI:
a) Dipole moment?
b) Geometry?
a) 0.38 D
b) linear
What is molecule (AB) H2:
a) Dipole moment?
b) Geometry?
a) 0 D
b) linear
What is molecule (AB2) H2O:
a) Dipole moment?
b) Geometry?
a) 1.85 D
b) bent
What is molecule (AB2) H2S:
a) Dipole moment?
b) Geometry?
a) 0.95 D
b) bent
What is molecule (AB2) CO2:
a) Dipole moment?
b) Geometry?
a) 0
b) linear
What is molecule (AB3)
NH3, NF3, BF3:
a) Dipole moment?
b) Geometry?
a) 1.47 D, 0.23 D, 0 D
b) trigonal pyramidal, trigonal pyramidal, trigonal planar
What is molecule (AB4)
CH4, CHCl3, CCl4
a) Dipole moment?
b) Geometry?
a) 0 D, 1.04 D, 0 D
b) all tetrahedral
What are the main postulates of VSEPR theory?
1) Shape of a molecule depends upon valence shell electron pairs(bonding and anti bonding) around central atom.
2] Pairs of electron in valence shell repel each other because their electron clouds are negatively charged.
3] These pairs of electrons tend to occupy such positions in spaces that minimize repulsion and thus maximize distance between them.
4) The valence shell is taken as a sphere with the electron pairs localizing on the spherical surface at maximum distance from one another.
5) A multiple bond is treated as if it is a single electron pair and two or three electron pairs of a multiple bond are treated as a single super pair.
6) Where two or more resonance structures can represent a molecule, the VSEPR model is applicable to any such structure.
What is the repulsive interaction of electron pairs order?
Lone pair-lone pair > lone pair-bond pair > bond pair- bond pair.
What is O=O bond enthalpy in O2?
498 kJ mol-1
What is N triple bond N bond enthalpy?
946.0 kJ mol^-1
What is average bond enthalpy of H2O?
464.5 kJ mol^-1
What is bond order?
Number of bonds between two atoms in a molecule.
What increases with increase in bond order?
Bond enthalpy
What decreases with bond order?
Bond length
What is resonance?
When a single Lewis structure can’t describe a molecule accurately, a no. of structures with similar energy, positions of nuclei, bonding and non-bonding pairs of electrons are taken as the canonical structures of the hybrid which describes the molecule accurately.
What is the example of resonance in O3 molecule?
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