1. pH and the pH Scale

2. Prepare to be... Absolutely pure water contains an equal number of free moving hydrogen ions and hydroxide ions. Where do these ions come from? If free moving ions are necessary to conduct electricity in water, then why can’t pure water conduct electricity? shocked!!!

3. pH and the pH Scale Question 1: Where do these ions come from? Pure water autoionizes. This means that water makes its own ions. For every water molecule that autoionizes, one hydrogen ion and one hydroxide ion is produced! # H 1+ = # OH 1- H 1+ + OH 1-  HOH

4. pH and the pH Scale Question 2: If free moving ions are necessary to conduct electricity in water, then why can’t pure water conduct electricity? In pure water, only 1 in every 555,555,556 water molecules autoionizes! Pure water just does not contain enough free moving ions to conduct electricity!

5. pH and the pH Scale Pure water contains an equal number of H 1+ ions and OH 1- ions. HOH H 1+ OH 1- HOH H 1+ OH 1-

6. pH and the pH Scale An acidic solution contains a greater number of H 1+ ions than OH 1- ions. HOH H 1+ OH 1- HOH H 1+ HOH

7. pH and the pH Scale An basic solution contains a greater number of OH 1- ions than H 1+ ions. HOH H 1+ OH 1- HOH OH 1- HOH

8. pH and the pH Scale All aqueous solutions contain hydrogen ion and hydroxide ions! HOH H 1+ OH 1- HOH H 1+ OH 1- Na 1+ Cl 1- NaCl (aq)

9. pH and the pH Scale A neutral solution contains an equal number of H 1+ ions and OH 1- ions. HOH H 1+ OH 1- HOH H 1+ OH 1- Na 1+ Cl 1- NaCl (aq)

10. pH and the pH Scale The pH scale is a scale from 0 to 14 that is used to measure the acidity or basicity (alkalinity) of a solution. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14     acid region base region neutral region strong acid strong base weak acid weak base

11. pH and the pH Scale Stomach "acid" has a pH around 1.0.

12. pH and the pH Scale Sea water has a pH around 8.5.

13. pH and the pH Scale Rainwater has a pH around 6.2.

14. pH and the pH Scale Human blood has a pH of 7.4.

15. pH and the pH Scale

16. A difference of 1 on the pH scale is really a tenfold [x10] difference in the concentration of H 1+ ions! 1) A solution of pH = 4 is ______ times ______ acidic than a solution of pH = 5. 2) A solution of pH = ______ is 10,000 times more acidic than a solution of pH = 7. 3) A solution of pH = 8 is ______ times ______ acidic than a solution of pH = 6. 10more 3 100less

17. pH and the pH Scale 4) A solution of pH = _____ is 1,000 times less acidic than a solution of pH = 8. 5) Acid rain is killing many lakes and ponds in the Adirondacks - the pH is too acidic. To treat symptoms, Ca(OH) 2 is added in order to adjust the pH. If a quantity of Ca(OH) 2 was added to a pond with a pH of 3.2 such that the water's hydronium ion concentration was changed by 1000 fold, then what would be the new pH of the pond? _____ 11 6.2