Chapter 9, Section 1 - Acids, Bases, and pH Acid - A compound that produces hydronium (H3O+) ions when dissolved in water. - Acids form H+ ions, which attach to water (H2O) to make hydronium (H3O+).
- Properties of acids...
- Taste sour.
- Cause indicators to change color.
- Conduct electric current.
- Are corrosive - can damage material, including skin.
Base - A compound that produces hydroxide (OH-) ions when dissolved in water. - Bases either give off OH- ions, or take hydrogen atoms from water to make OH- ions.
- Metal hydroxides - Bases that contain a metal ion and a hydroxide ion. (ex. - NaOH) These are strong bases.
- Properties of bases...
- Taste bitter.
- Feel slippery (like soap).
- Cause indicators to change color.
- Conduct electric current.
- Can damage skin.
Indicator - A compound that changes color, depending on conditions (such as pH). - Blue litmus paper turns red in acid.
- Red litmus paper turns blue in base.
Electrolyte - A substance that conducts electric current when dissolved in water.
Strong Acids & Bases - All of the molecules dissolved in water ionize (form ions).
- Are strong electrolytes - they produce as many ions as the acid/base can possibly form.
- Metal hydroxides are strong bases.
Weak Acids & Bases - Do not ionize completely.
- Form equilibrium systems (reaction to form ions is reversible).
- Are weak electrolytes (do not conduct electricity as well as strong acids/bases).
Safety Concerns - Concentrated acids/bases can be damaging to the skin.
 - Vapors can harm eyes, mouth and lungs.
- Precautions...
- safety goggles, gloves, lab aprons
pH - A value used to express acidity or basicity (alkalinity).
- The pH scale ranges from 0 to 14.
- Below 7 is acidic.
- 7 is neutral.
- Above 7 is basic.
- pH is a measure of the concentration of H3O+ ions => related to molarity.
- The concentration of H3O+ ions in pure water is 1x10-7 M. The pH is the negative of the power of 10, so 7 in this case.
- The concentration of H3O+ ions in apple juice is 1x10-3 M. So, its pH is is 3.
- Each whole number difference in pH equals a 10x change in acidity/basicity.
- pH can be measured with pH paper or with electrical pH meters.
Homework: Pg. 300 #1-6, 8-10.
Chapter 9, Section 2 - Reactions of Acids with Bases Neutralization Reaction - The reaction of an acid and a base, which produces water and a salt.
NaOH => Na+ + OH-
- Reaction of acid and base ions...
H3O+ + Cl- + Na+ + OH- => Na+ + Cl- + 2H2O
Spectator Ions - Ions that don't change during the reaction.
If the water is removed, the Na+ and Cl- will combine to form NaCl (salt).
Salt - An ionic compound formed when a metal ion replaces the hydrogen in an acid.
If there is...
...more acid than base => solution will be acidic.
...more base than acid => solution will be alkaline (basic).
...the same amount of acid and base => solution will be neutral.
Titration - The process of adding small amounts of one solution to another, in the presence of an indicator, to determine concentration.
Ex. - Bromothymol Blue is yellow in acids, blue in bases.
Start with some acid and bromothylmol blue (yellow solution).
Add base, a little at a time, until the solution changes to blue (at pH 7).
Salts can be almost any combination of cations and anions (except hydroxides and oxides - which are bases).- Salts have many uses.
- Many occur naturally, some are made by chemical reactions.
- Salts provide ions that are needed by the body...
- Ca+2 are used in bones and teeth, and allow muscles and nerves to work properly.
- K+ and Na+ are needed for nerves to function.
- Cl- balance the positive ions in the body.
- PO4-3 is used in DNA and transporting energy.
Homework: Pg. 306 #1-7.
Chapter 9, Section 3 - Acids, Bases, and Salts in the Home Cleaning Products help water mix with oily substances. - Soap - A substance used as a cleaner that dissolves in water.
- Salts of Na+ or K+.
- Can dissolve in oil or water.
- Forms an emulsion that can be rinsed away.
- Has a polar end (metal ion) and a nonpolar end (fatty acids).
- Water is attracted to the polar end.
- Oil is attracted to the nonpolar end.
- Detergent - A water-soluble cleaner that can emulsify dirt and oil.
- Salts of Na+ or K+ or sometimes NH4+.
- Similar to soap, but with a SO3- group at the charged end, instead of a CO2- group.
- Hard Water - Water with dissolved Mg+2, Ca+2, and Fe+3 ions.
- Soap combines with ions in hard water to make soap scum (insoluble salt).
- Detergents don't form soap scum.
- Ammonia - A weak base.
- Used in glass cleaners - can remove fingerprints and oily smears.
- Bleach - A compound used to whiten (remove color).
- Basic solution of NaOCl (sodium hyopchlorite) - changes substances to colorless forms by releasing oxygen.
- NEVER add the following to chlorine bleach...
- ACID - produces chlorine gas, which is deadly.
- AMMONIA - produces toxic chloramine gas (NH2CL).
- Bleach is used as a disinfectant (substance that kills harmful bacteria or viruses).
Personal Care & Food Items - Healthcare Items
- Vitamin C = Ascorbic Acid
- Used for growth and repair.
- Antacids - Weak bases that neutralize stomach acids.
- NaHCO3 (sodium hydrogen carbonate = baking soda)
- Mg(OH)2 (magnesium hydroxide = milk of magnesia)
- Shampoo
- Adjusted for pH
- Higher pH = better at cleaning oils from hair.
- Lower pH = better at protecting hair.
- Acid Antioxidants
- Acids can prevent oxidation by reacting with oxygen before it can react with other molecules.
- In the Kitchen
- Acids
- vinegar & citric acid - used in marinades & to tenderize meat
- acids help turn milk into yogurt
- Salts
- Baking soda (sodium bicarbonate) forms CO2 gas at high temps => used in baking to make bread/cake rise.
- Bases
- Drain cleaner (sodium hydroxide) breaks down grease and other things that cause clogs.
Homework: Pg. 313 #1-7.
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