Energy and Entropy in Solution Formation

Sample Problem 13.1 shows how to predict solubility based on the overall polarity of the solute and the solvent. 

Strategy Consider the structure of each solute to determine whether or not it is polar. For molecular solutes, start with a Lewis structure and apply the VSEPR theory [M Section 9.1]. We expect polar solutes, including ionic compounds, to be more soluble in water. Nonpolar solutes will be more soluble in benzene. 

With four electron domains around the central atom, we expect a tetrahedral arrangement. A symmetrical arrangement of identical bonds results in a nonpolar molecule. 

Crossed arrows can be used to represent the individual bond dipoles [ W Section 9.2]. This molecule is polar and can form hydrogen bonds with water. 

Think About It Remember that molecular formula alone is not sufficient to determine the shape or the polarity of a polyatomic molecule. It must be determined by starting with a conect Lewis structure and apptying the VSEPR theory. 

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