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What is pH?

What is pH?. Concentration and hydrogen ions and hydroxide ions are a measure of The acidity and alkalinity of a solution. How was the concept of pH developed?. H 2 O is a molecule. Therefore, pure water does not conduct electricity. Or does it?.

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What is pH?

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  1. What is pH? Concentration and hydrogen ions and hydroxide ions are a measure of The acidity and alkalinity of a solution.

  2. How was the concept of pH developed? H2 O is a molecule. Therefore, pure water does not conduct electricity.

  3. Or does it? When pure water was found to conduct very small currents of electricity, the self-ionization of water was discovered.

  4. Self-ionization of water H2 O  H+ + OH- Water can dissociate into Hydronium ions and hydroxide ions.

  5. How much dissociation is there? [H+] = 1 x 10-7 M [OH-] = 1 x 10-7 M Therefore: [H+] x [OH-] = 1 x 10-14 M

  6. [h+]x [OH-] = 1 x 10-14 M Is called the Ion-product constant AKA: kw

  7. Ion product constant Kw = 1 x 10-14 M

  8. acidity is a measure of the [H+] of a solution. If the [H+] of a solution is 1.0 x 10-5M, is the solution acidic, basic or neutral? 1.0x 10-5 M is greater than 1.0 x 10-7 M Therefore the solution is acidic

  9. Practice: acidic, basic or neutral? • [H+] = 6.0 x 10-10M • [H+] = 2.0 x 10-7 M • [OH-] = 1.0 x 10 -7 M

  10. Solve these problems usingkw = [H+] x [OH-] and determine whether solution is acidic, neutral or basic • [OH-] = 1 x 10-3 2. [OH-] = 2.0 x 10-11 3. [OH-] = 3.5 x 10-7

  11. The pH scale Ranges from 0 -14. 0 – 6.9 = acidic 7.0 = neutral 7.1 – 14.0 = basic (alkaline)

  12. So where do these numbers come from? pH = - log [H+] That’s where they come from!

  13. What is the pH? • [H+] = 1.0 x 10-4 M • [H+ ] = 1.0 x 10 -2 M • [H+] = 1.0 x 10 -10 M • [H+] = 1.0 x 10-7 M • [H+] = 1.0 x 10-14 M

  14. answers • 4 • 2 • 10 • 7 • 14

  15. Get your calculators out and practice. • [H+] = 0.0045 M • [H+] = 8.7 x 10-6 M • [H+] = 0.0015M • [H+] = 1.2 x 10-3 M

  16. answers • PH = 2.35 • PH = 5.06 • PH = 2.82 • PH = 2.92

  17. Find the pH and determine if it is acid basic or neutral • [H+] = 1.5 x 10-9 • [H+] = 3.4 x 10-2 • [H+] = 5.5 x 10-11 • [H+] = 1.0 x 10-7

  18. You can also calculate ph from [OH- ] If you are given [OH-] use [H+] = 1 x 10-14 [OH-] To find hydrogen ion concentration then solve for pH pH = –log [H+]

  19. Let’s practice Calculate the pH of a solution with a [OH-] of 3.5 x 10-9

  20. Exit Slip: Your Name here…… • Find the pH of a solution with an hydroxide concentration of [OH-] = 2.9 x 10-5 2. A solution has a hydrogen ion concentration of [H+] = 5.0 x 10 -12. Is it acidic, basic or neutral?

  21. Brainpop

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