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PH. Definitions and Formulas The pH scale is defined as the negative log of the concentration of H + : pH = -log[H + ] The pOH scale is defined as the.

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Presentation on theme: "PH. Definitions and Formulas The pH scale is defined as the negative log of the concentration of H + : pH = -log[H + ] The pOH scale is defined as the."— Presentation transcript:

1 pH

2 Definitions and Formulas The pH scale is defined as the negative log of the concentration of H + : pH = -log[H + ] The pOH scale is defined as the negative log of the concentration of OH -, [OH - ]. pOH = -log[OH - ] With this scale, calculating the pOH can be done in the same manner as the pH scale. pH + pOH = 14

3 Examples What is the pH of a solution that contains 25 g of hydrochloric acid (HCl) dissolved in 1.5 L of water?

4 Quiz 1.Determine the pH of a.0034 M HNO 3 solution. 2.Determine the pOH of the solution in #1. 3.What is the pH of a 2.4 x 10 -5 M HCl solution?

5 Auto-Ionization of Water [OH - ]= K w [H 3 0 + ]= K w [H 3 0 + ] [OH - ] Example: What is the hydroxide ion concentration in an aqueous solution that is 4.0 x 10 -5 M H 3 0 + ? [OH-] = (1.0 x 10 -14 ) (4.0 x 10 -5 ) =2.5 x 10 -10 M ion product constant for water  Kc (55.5M) = [H+][OH-] = Kw  K w = [H 3 0+] [OH-]  K w = 10 -14 In water, Kc= [H+][OH-] 55.5 M

6 Practice What is the hydronium ion concentration in an aqueous solution containing 3.5 x 10 -7 OH - ? [H 3 0 + ] = (1.0 x 10 -14 ) (3.5 x 10 -7 ) =2.9 x 10 -8 What is the hydroxide ion concentration in an aqueous solution containing 8.34 x 10 -12 H 3 0 + ? [OH - ] = (1.0 x 10 -14 ) (8.34 x 10 -12 ) =1.20 x 10 -3

7 Strong Acids dissociate completely in water to form hydronium ion(s) Examples –HCl –HNO 3 –H 2 SO 4

8 Strong Bases dissociate completely in water to form hydroxide ions Examples: –NaOH –KOH –Ca(OH) 2


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