Molecular geometry polarity and

What is the approximate value of the bond angle indicated  

Molecular geometry is tremendously important in understanding the physical and chemical behavior of a substance. Molecular polarity, for example, is one of the most important consequences of molecular geometry, because molecular polarity influences physical, chemical, and biological properties. Recall from Section 8.4 that a bond between two atoms of different electronegativities is polar and that a diatomic molecule containing a polar bond is a polar molecule. Whether a molecule made up of three or more atoms is polar depends not only on the polarity of the individual bonds, but also on its molecular geometry. 

Each of the CO2 and HiO molecules contains two identical atoms bonded to a central atom and two polar bonds. However, only one of these molecules is polar. To understand why, think of each individual bond dipole as a vector. The overall dipole moment of the molecule is determined by vector addition of the individual bond dipoles. 

In the case of CO2, we have two identical vectors pointing in opposite directions. When the vectors are placed on a Cartesian coordinate system, they have no y component and their t components are equal in magnitude but opposite in sign. The sum of these two vectors is zero in both the, v and y directions. Thus, although the bonds in COo are polar, the molecule is nonpolar. 

---

Strategy Recall the discussion in Chapter 7, Sections 7.1 to 7.3, where the principles of resonance, molecular geometry, and polarity were considered. 

If process conditions are such that the ideal gas equation of state is a poor approximation, a more complex species-specific equation of state must be used. Most such equations, including the Soave-Redlich-Kwong (SRK) equation of state, contain adjustable parameters that depend on the critical temperature and pressure of the species and possibly other factors that depend on the molecular geometry and polarity of the species. 

Use Figure 4-la and your knowledge of molecular geometry and polarity to determine whether or not the following substances are ionic compounds, non-polar molecular compounds, or polar molecular compounds. 

Skill 7.7 Using VSEPR theory to explain molecular geometry and polarity... 

Enzymes are proteins that act as catatysts for specific biochemical reactions in living systems. The reactants in enzyme-catalyzed reactions are called substrates. Thousands of vital processes in our bodies are catalyzed by many different enzymes. For instance, the enzyme carbonic anhydrase catalyzes the combination of CO2 and water (the substrates), facilitating most of the transport of carbon dioxide in the blood. This combination reaction, ordinarily slow, proceeds rapidly in the presence of carbonic anhydrase a single molecule of this enzyme can promote the conversion of more than 1 million molecules of carbon dioxide each second. Each enzyme is extremely specific, catalyzing only a few closely related reactions—or, in many cases, only one particular reaction—for only certain substrates. Modem theories of enzyme action attribute this to the requirement of very specific matching of shapes (molecular geometries) and polarities for a particular substrate to bind to a particular enzyme (Figure 16-19). 

Chemical bonding—molecular geometry and polarity (interactive). 

SECTION 9.2 Molecular Geometry and Polarity The bond dipoles in the cis isomer do not cancel one another, so c/s-dichloroethylene is polar ... 

Molecular geometry and polarity [W Section 9.2] MPEG Content... 

Molecular Geometry and Polarity Valence Bond Theory Hybridization of Atomic Orbitals... 

---