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The Effect of Structure on Acid-Base Properties. Bronsted Lowry Acids. There are two factors that determine whether a molecule containing an X-H bond will behave as a Bronsted-Lowry acid: 1) strength of the bond 2) polarity of the bond. Hydrogen Halides.
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Bronsted Lowry Acids • There are two factors that determine whether a molecule containing an X-H bond will behave as a Bronsted-Lowry acid: 1) strength of the bond 2) polarity of the bond
Hydrogen Halides • HF>HCl>HBr>HI (decreasing polarity) • HF>HCl>HBr>HI (decreasing bond strength) • HF is the only weak acid due to its unusually high bond strength.
Oxyacids • Cl>Br>I>CH3 (decreasing electronegativity) • HOCl>HOBr>HOI>HOCH3 (decreasing acid strength) • As the electronegativity of X increases, the ability to draw electrons to it increases. This weakens the O-H bond and makes the proton more readily produced.
Oxyacids Continued • As the number of oxygen atoms in an acid increases, the strength of the acid increases. • Oxygen has a high electronegativity and draws the electrons away from the nonmetal and the O-H bond resulting in the proton being more readily produced. • Example: HClO4>HClO3>HClO2>HClO
Which of the following is the strongest acid? 10 • HIO3 • HBrO3
Which of the following is the strongest acid? 10 • HNO3 • HNO2
Which of the following is the strongest acid? 10 • HOCl • HOI
Which is the strongest acid? 10 • H3PO3 • H3PO4