1. Acids-Bases and Indicators Chemistry 1105

2. background An extremely large class of reactions Found in  Biochemistry –  Cleaning products  Industrial fabrication  foods

3. Theory Historically known but not understood Gay-Lussac defined them in 1814  But in terms of each other  Svante Arrhenius won the Nobel Prize for his definition the Acids and Base work  This is still the one most often used for acids and bases

4. Definitions Arrhenius Acid  Releases hydrogen ion  Produces H 3 O +  HNO 3 + H 2 O → H 3 O + + NO 3 - Arrhenius BASE  Releases OH ion in water  NaOH + H 2 O  Na + + OH - + H 2 O

5. Strong vs. Weak Strong Acid/Base  Completely Dissociates  No Equilibrium  No Reactants Are Observed After Reaction  HNO 3 + H 2 O → H 3 O + + NO 3 -  NaOH + H 2 O → Na + + OH - + H 2 O  Only Few Strong Acids And Bases

6. Strong vs. Weak Weak Acid/Base  Partially Dissociates  Reaction Is In Equilibrium  Products And Reactants Observed  HF + H 2 O ↔ H 3 O + + F -

7. pH Reference is Water  Water is amphoteric- Characteristics of both acid and base  H 2 O + H 2 O ↔ H 3 O+ + OH - In Pure Water,  [H 3 O+] = 1.0 x 10^(-7)  [OH - ] = 1.0 x 10^(-7) pH = -log [H 3 O+] = -log(1.0 x 10^(-7)) = 7 Most water is not 7 Our is between 4-5

8. history Brønsted and Lowery in 1923 Showed that an acid or a base could be donors and acceptors with a H present HF + H2O ↔ H3O+ + F- And as in water  H 2 O ↔ H+ + OH - Where HO- a Lewis base and H+ the Lewis acid.

9. Indicators Complex molecules that absorb light at different wavelengths Acid or a base and it reacts with the compound Changes the wavelength and thus the color

10. Indicators Iitmus paper- made from lichens  Red, acid,  Blue, base  Lots of possible indicators and more daily  Thymolblue  Methyl orange  Yamada is a universal indicator Red to orange in acid, green at neutral, and blue to indigo in acid

11. Acid Content The number of hydrogen ions available in the acid  Sulfuric acid H 2 SO 4 ACID CONCENT =2  HCl = 1  Measured by Titrations

12. Titrations Titration is a procedure used to determine the concentration of an acid or base. Neutralization HCl+NaOH  NaCl+H 2 O Need to know  The initial concentration of the base  The initial volume of acid  The amount of base that is used to neutralize the acid

13. Titration Moles of acid = moles of the base Changes pH starts acidic goes basic At neutralization of strong acid and strong base =7 Neutral. Not always 7, Depends on the acid and the base

14. Experimental Procedure Acid and Base In 5 wells 3 drops of X and 3 drops of Y Using litmus paper blue and red record reaction One drop yamada, thymolblue, methy orange pH scale  10 wells add one drop of each of the std solutions1-10  Then add I drop yamada, record color

15. pH scale Determine the pH of the X and Y Now test pH using Yamada  Nitric acid (0.1 M)  Acetic acid (0.1 M)  Ammonia hydroxide (0.1 M)

16. Titration Use unknown acid from above  Add one drop in each of 10 wells Add one drop Yamada to each well number 1 add 1 drop NaOH Well number 2 add 2 drops etc. to ten with 10 drops Now repeat with the other unknown base and titrate with acid

17. 1) Place 3 drops of solution X Place 3 drops of solution Y 2) Test pH with red and blue litmus paper, Yamada, bromocresol, and thymol blue Indicators. 3)Place 5 drops of each pH solution 1-10 in Separate wells. Add one drop of YAMADA indicator 4)Using the scale determine pH of solutions X and Y. 5) Take 5 drops of 0.1M nitric acid and 5 drops of 0.1M acetic acid and test with Yamada indicator Creating a pH scale 1 2 3 4 5 6 7 8 9 10 NOTE: THE COLORS ARE JUST AN EXAMPLE DO NOT REPRESENT REAL COLORS IN THE EXPERIMENT 1 X Y

18. How should it look?

19. Titration In 12 different clean wells place: 1 drop of BASE (unknown X or Y) to each wells 1 drop of indicator Titrate with base HCl 0.005M adding 1 drop to well 1 2 drops to well 2 3 drops to well 3 Continue until you find the green neutral color

20. Titration Add 0.005M NaOH In 12 different clean wells place: 1 drop of ACID (unknown X or Y) to each wells 1 drop of indicator Titrate with base NaOH 0.005M adding 1 drop to well 1 2 drops to well 2 3 drops to well 3 Continue until you find the green neutral color

21. Titration In 12 different clean wells place: 1 drop of ACID (unknown X or Y) to each wells 1 drop of indicator Titrate with base NaOH 0.005M adding 1 drop to well 1 2 drops to well 2 3 drops to well 3 Continue until you find the green neutral color

22. Acid and Base Which well is neutralization How many drops Do report (Note: Each drop is 0.05 mls)