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Journal 2/7/14

Journal 2/7/14. What does ionization of water mean?. Objective Tonight’s Homework. To learn how we measure acidity. look up the pH of 5 things. We'll add this as a class list. Notes on pH. Last time, we said that for pure water: [H + ] = 1.0×10 −7 M

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Journal 2/7/14

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  1. Journal 2/7/14 What does ionization of water mean? Objective Tonight’s Homework To learn how we measure acidity look up the pH of 5 things. We'll add this as a class list

  2. Notes on pH Last time, we said that for pure water: [H+] = 1.0×10−7 M If we put an acid in water, our concentration of H+ will increase, because H+ will break off the acid and go into the water. The stronger the acid, the more H+ we’ll have.

  3. Notes on pH Last time, we said that for pure water: [H+] = 1.0×10−7 M If we put an acid in water, our concentration of H+ will increase, because H+ will break off the acid and go into the water. The stronger the acid, the more H+ we’ll have. If we put a base in water, the OH- from the base will absorb some of the H+ already there and we’ll have less H+. The stronger the base, the less H+ we’ll have.

  4. Notes on pH However, writing everything in scientific notation is a bit tedious. So scientists defined something called the “potential of hydrogen” or “pH” for short. pH = -log[H+]

  5. Notes on pH However, writing everything in scientific notation is a bit tedious. So scientists defined something called the “potential of hydrogen” or “pH” for short. pH = -log[H+] For pure water: pH = -log[1.0×10−7] = 7.00 A pH of 7 is defined as neutral.

  6. Notes on pH If we increase our concentration of [H+], our solution becomes more acidic and our pH lower. Example: A solution has [H+] = 1.0×10−4. If we calculate the pH, we get 4. Every time our pH gets smaller by 1, the concentration of our [H+] goes up by a factor of 10. In other words, a liquid with a pH of 2 would be 10 times more acidic than a liquid with a pH of 3.

  7. Notes on pH We can also define something called pOH. pOH is the opposite of pH. It tells us the concentration of [OH-]. We calculate it the same way we do pH. As pH gets larger, pOH gets smaller. Given pH and pOH are inverses, the following is always true: pH + pOH = 14

  8. Practice Calculate the pH of each solution below: 1) [H+] = 1.4×10−3 M 2) [H+] = 2.5×10−10 M 3) [H+] = 6.1M 4) [OH-] = 3.5×10−2 M 5) [OH-] = 8×10−11 M 6) [OH-] =5.0 M 7) pOH = 10.5 8) pOH = 2.3 Calculate [H+] for each solution: 9) pH = 7.41 10) pH = 15.3 11) pH = -1.0 12) pH = 3.2 13) pOH = 5.0 14) pOH = 9.6

  9. Exit Question #17 What would a pH of 0 mean? a) A concentration of zero b) An acid concentration of 1 M c) A base concentration of 1 M d) An acid and base concentration of 1 M e) All of the above f) None of the above

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