1. Acids, Bases, & Salts

2. What is an ACID? pH less than 7 Neutralizes bases
Forms H + ions in solution
Corrosive-reacts with most metals to form hydrogen gas
Good conductors of electricity

3. Acids Generate Ions
HNO3 + H2O  H3O NO3

4. Weak vs. Strong Acids
Weak Acids do not ionize completely: Acetic, Boric, Nitrous, Phosphoric, Sulfurous
Strong Acids ionize completely: Hydrochloric, Nitric; Sulfuric, Hydriodic

5. Common Acids HCl- hydrochloric- stomach acid
H2SO4- sulfuric acid - car batteries
HNO3 – nitric acid - explosives
HC2H3O2- acetic acid - vinegar
H2CO3-carbonic acid – sodas
H3PO4- phosphoric acid -flavorings

7. What is a BASE? pH greater than 7 Feels slippery
Dissolves fats and oils
Usually forms OH- ions in solution
Neutralizes acids

8. Weak vs. Strong Bases
Weak Bases: ammonia; potassium carbonate, sodium carbonate
Strong Bases: sodium hydroxide; sodium phosphate; barium hydroxide; calcium hydroxide

9. Common Bases NaOH- sodium hydroxide (LYE) soaps, drain cleaner
Mg (OH)2 - magnesium hydroxide-antacids
Al(OH)3-aluminum hydroxide-antacids, deodorants
NH4OH-ammonium hydroxide- “ammonia”

10. Types of Acids and Bases
In the 1800’s chemical concepts were based on the reactions of aqueous solutions.
Svante Arrhenius developed a concept of acids and bases relevant to reactions in H2O.
Arrhenius acid – produces hydrogen ions in water.
Arrhenius base – produce hydroxide ions in water.

11. A broader ,more modern concept of acids and bases was developed later.
Bronsted-Lowry acid- donates a hydrogen ion in a reaction.
Bronsted – Lowry base – accepts a hydrogen in a reaction.

12. Conjugate acid- compound formed when an base gains a hydrogen ion.
Conjugate base – compound formed when an acid loses a hydrogen ion.

13. pH Scale

14. pH of Common Substances
Timberlake, Chemistry 7th Edition, page 335

15. pH testing There are several ways to test pH
Blue litmus paper (red = acid)
Red litmus paper (blue = basic)
pH paper (multi-colored)
pH meter (7 is neutral, <7 acid, >7 base)
Universal indicator (multi-colored)
Indicators like phenolphthalein
Natural indicators like red cabbage, radishes

16. pH indicators
Indicators are dyes that can be added that will change color in the presence of an acid or base.
Some indicators only work in a specific range of pH
Once the drops are added, the sample is ruined
Some dyes are natural, like radish skin or red cabbage

17. Reactions with indicators
Acid color
Neutral color
Base color
Phenolphthalein
Colorless
Faint pink
Dark pink
Bromthymol blue
Yellow
Green
Blue
Litmus
Red
-----

18. Paper testing Paper tests like litmus paper and pH paper
Put a stirring rod into the solution and stir.
Take the stirring rod out, and place a drop of the solution from the end of the stirring rod onto a piece of the paper
Read and record the color change. Note what the color indicates.
You should only use a small portion of the paper. You can use one piece of paper for several tests.

19. pH meter Tests the voltage of the electrolyte
Converts the voltage to pH
Very cheap, accurate
Must be calibrated with a buffer solution

20. Buffers
A buffer is a solution that resists changes in pH when small amounts of acids and bases are added.

21. Situations in which pH is controlled
“Heartburn”
Planting vegetables and flowers
Fish Tanks and Ponds
Blood
Swimming pools

22. Acids and Bases in Solution
HCl + H20  H3O Cl (more hydronium ions, more acidic)
NaOH in water  Na OH (more hydroxide ions, more basic)
NaOH + HCl  NaCl + HOH Acid + Base yields type of salt and water
NH3 + H20  NH OH ammonia gas + water yields ammonium and hydroxide ions

23. Acid Rain
Pollution in the air (sulfur dioxide, carbon dioxide, nitrogen dioxide) combines with water to form various acids. .

24. Rapid changes in pH can kill fish and other organisms in lakes and streams.
Soil pH is affected and can kill plants and create sinkholes

28. What is a SALT?
A salt is a neutral substance produced from the reaction of an acid and a base.
Composed of the negative ion of an acid and the positive ion of a base.
One of the products of a Neutralization Reaction
Examples: KCl, MgSO4, Na3PO4

29. Neutralization Reaction
A neutralization reaction is the reaction of an acid with a base to produce salt and water.
Example
H2SO4 + NaOH  NaHSO4 + H2O

30. Digestion and pH
Digestion-process by which foods are broken down into simpler substances.
Mechanical digestion-physical process in which food is torn apart (mouth)
Chemical digestion- chemical reactions in which large molecules are broken down into smaller molecules. (stomach and small intestines)

31. pH in the Digestive System
Mouth-pH around 7. Saliva contains amylase, an enzyme which begins to break carbohydrates into sugars.
Stomach- pH around 2. Proteins are broken down into amino acids by the enzyme pepsin.
Small intestine-pH around 8. Most digestion ends. Small molecules move to bloodstream toward cells that use them

32. Digestive system mouth esophagus stomach small intestine
large intestine

33. ACID-BASE REACTIONS Titrations
H2C2O4(aq) NaOH(aq) --->
acid base
Na2C2O4(aq) H2O(liq)
Carry out this reaction using a TITRATION.
Oxalic acid,
H2C2O4

34. Setup for titrating an acid with a base

35. Titration 1. Add solution from the buret.
2. Reagent (base) reacts with compound (acid) in solution in the flask.
Indicator shows when exact stoichiometric reaction has occurred. (Acid = Base)
This is called NEUTRALIZATION.

36. Acids, Bases, and Salts The End