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Pure Water is Neutral

Pure Water is Neutral. Pure water contains small, but equal amounts of ions: H 3 O + and OH - H 2 O + H 2 O H 3 O + + OH - hydronium hydroxide ion ion 1 x 10 -7 M 1 x 10 -7 M. H 3 O +. OH -. [H 3 O + ] = [OH - ] = 1 x 10 -7 M

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Pure Water is Neutral

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  1. Pure Water is Neutral Pure water contains small, but equal amounts of ions: H3O+ and OH- H2O + H2O H3O+ + OH- hydronium hydroxide ion ion 1 x 10-7 M1 x 10-7 M H3O+ OH-

  2. [H3O+ ] = [OH-] = 1 x 10-7 M • Since they are equal, a neutral solution results from water • Kw = [H3O+ ] x [OH-] = 1 x 10-14M2 • Kw is called the “ion product constant” • The equation is applicable to pure water and aqueous solutions

  3. pH and pOH • pH = -log [H3O+] • pOH = -log [OH-] • pH + pOH = 14 • [H3O+] = antilog -pH

  4. 100 10-1 10-3 10-5 10-7 10-9 10-11 10-13 10-14 14 13 11 9 7 5 3 1 0 10-14 10-13 10-11 10-9 10-7 10-5 10-3 10-1 100 [H+] pH 0 1 3 5 7 9 11 13 14 Acidic Neutral Basic pOH [OH-]

  5. Using Kw The [OH- ] of a solution is 1.0 x 10- 3M. What is the [H3O+]? Kw = [H3O+ ] [OH- ] = 1.0 x 10-14 M2 [H3O+] = 1.0 x 10-14 M2 [OH-] [H3O+] = 1.0 x 10-14 M2= 1.0 x 10-11 M 1.0 x 10- 3 M

  6. Using the Calculator 1.0 x 10 -14 1.0 x 10-3 Enter1.0 EE +/- 14 1.0 EE+/- 3 = 1.0 x 10 -11

  7. Find the hydroxide ion concentration of 3.0  10-2 M HCl. [H3O+][OH-] = 1.0  10-14 [3.0  10-2][OH-] = 1.0  10-14 [OH-] = 3.3  10-13 M Acidic or basic? Acidic

  8. pH In the expression for [H3O+] 1 x 10-exponent the exponent = pH [H3O+] = 1 x 10-pH M

  9. Some [H3O+] and pH [H3O+] pH 1 x 10-5 M 5 1 x 10-9 M 9 1 x 10-11M 11

  10. Learning Check The pH of a soap is 10. What is the [H3O+] of the soap solution? [H3O+] = 1 x 10-pH M = 1 x 10-10 M

  11. pH on the Calculator [H3O+] is 4.5 x 10-6 M pH = ? pH = -log [H3O+] pH = 4.5 EXP(or EE) 6 +/- LOG +/- = 5.3

  12. pH Scale • What is the pH of 0.050 M HNO3? pH = -log[H3O+] pH = -log[0.050] pH = 1.3 Acidic or basic? Acidic

  13. pH Scale • What is the molarity of HBr in a solution that has a pOH of 9.6? • [H3O+] = antilog -pH pH + pOH = 14 pH + 9.6 = 14 pH = 4.4 pH = -log[H3O+] 4.4 = -log[H3O+] -4.4 = log[H3O+] [H3O+] = 4.0  10-5 M HBr Acidic

  14. Learning Check Identify each solution as 1. acidic 2. basic 3. neutral A. _1__ HCl with a pH = 1.5 B. _2__ Pancreatic fluid [H+] = 1 x 10-8 M C. _1__ Sprite soft drink pH = 3.0 D. _3__ pH = 7.0 E. _1__ [OH-] = 3 x 10-10 M F. _2__ [H+] = 5 x 10-12 M

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