Results Tables neatly filled out with data Post Lab Questions Typed answers to t

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Results Tables neatly filled out with data Post Lab Questions Typed answers to the Post Lab questions. Note that single sentence answers will not suffice. State the answer to the question followed by a brief description of the evidence supporting that answer. Post Lab Questions: 1. Describe the underlying principle of VSEPR theory in your own words. 2. Explain why two compounds with the same generic formula, NH_3 and BH_3, have different molecular geometries. 3. Why are the structures of H_2S and H_2O so similar? Why are the structures of CH_4 and SiH_4 so similar? 4. Although PH_3 and BH_3 both contain bonds of similar polarity, one molecule is polar while the other is nonpolar. Explain. 5. Write a detailed procedure in your own words for converting a chemical formula into a Lewis structure and how to determine the geometry and polarity from this Lewis structure.

Explanation / Answer

1) VSEPR theory

This theory considers the electrons pairs and their repulsions around the central atom of the molecule.

Thus the number of elecronpairs decide the basic geometrical arrangement aorund the central atom. they do so to minimize the repulsions.

* the electronpairs canbe bonded or lone pairs(non-bonded)

*the presence of lone pairs of electrons distract the geometrical shape of molecule.

*The repulsions beween the lonepairs-lone pairs > lone pairs -bond pairs > bond pairs -bond pairs

2) NH3 ha 3 bond pairs and one lone pair, where as BH3 has 3 bond pairs only.

So their orbital geometries are different.

3) H2O and H2S . In both of them the cental atom is of VIA group, have same number of lone pairs and bond pairs.

thus they have same shape. Similarly in CH4 and SiH4 the central atoms belong to IV groupand thus have same number of (four) bond pairs. thus have similar shapes and geometry.

4) PH3 has 3 lone pairs and bond pairs , so its molecular geometry is trigonal pyramidal and electron geometry is tetrahedral.due to the presence of lone pair and unsymmetrical structure it is polar.

Bh3 has only 3 bond pairs and is planar trigonal .therefore it is symmetric structure thus is non-polar.

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