1. Strengths of Acids and Bases Integrated Science II

2. Strength Degree to which they form ions

3. Strong Acids Strong Acids: When they are placed in water, all the molecules of a strong acid dissociate, putting lots of H+ ions in the water. These substances have very low pH. HCl + H 2 O  H 3 O + + Cl -

4. Strong Acids HClHClO 4 H 2 SO 4 HI HNO 3 HBr

5. Weak Acids Weak Acids: When they are placed in water, only some of the molecules of a weak acid dissociate, putting some H+ ions in the water, but not as many as the strong acids. These substances have pH of less than 7 (but usually greater than 3 or 4) HC 2 H 3 O 2 + H 2 O  H 3 O + + C 2 H 3 O 2 -

6. Weak Acids H 3 PO 4 – phosphoric acid H 2 CO 3 – carbonic acid Both of these weak acids are found in soft drinks

7. Strong Bases Strong Bases: When they are placed in water, all the molecules of a strong base dissociate, putting lots of OH- ions in the water. The OH- ions lower the number of free H+ ions. These substances have very high pH. NaOH  Na + + OH -

8. Strong Bases NaOHCsOH KOHCa(OH) 2 RbOHBa(OH) 2

9. Weak Bases Weak Bases: When they are placed in water, only some of the molecules of a weak base dissociate, putting some OH- ions in the water, but not as many as the strong bases. These substances have pH of greater than 7 (but usually less than 10 or 11) NH 3 (g) + H 2 O  NH 4 + + OH -

10. Strong & Weak Acids and Bases

11. Strong and weak is an indication of strength. Dilute and concentrated is an indication of concentration.

12. pH scale pH is a measure of the concentration of hydronium ions (H 3 O + ) in a solution pH scale ranges from 0 to 14 –pH < 7 is acidic –pH > 7 is basic –pH = 7 is neutral

13. Decreasing pH As pH decreases, H 3 O + Concentration OH - concentration

14. Increasing pH H 3 O + Concentration As pH increases, OH - concentration

15. Using pH pH tells us the condition of the water and its suitability for swimming.

16. pH scale

17. Neutralization Neutralization – is a chemical reaction between an acid and a base. –During a neutralization reaction, hydronium ions (H 3 O + ) from the acid combine with the hydroxide ions (OH - ) from the base to produce water.

19. Salts Salt is a compound formed when the negative ions from an acid combine with the positive ions from a base. HCl + H 2 O  H 3 O + + Cl - NaOH  Na + + OH -

20. pH in the chemistry of nature