The Chemistry of Acids and Bases : The Chemistry of Acids and Bases Chemistry I – Chapter 19
Chemistry I HD – Chapter 16
ICP – Chapter 23 SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNcheck "Background Printing")!
Acid and Bases : Acid and Bases
Acid and Bases : Acid and Bases
Acid and Bases : Acid and Bases
Acids : Acids Have a sour taste. Vinegar is a solution of acetic acid. Citrus
fruits contain citric acid. React with certain metals to produce hydrogen gas. React with carbonates and bicarbonates to produce carbon
dioxide gas Have a bitter taste. Feel slippery. Many soaps contain bases. Bases
Some Properties of Acids : Some Properties of Acids Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule)
Taste sour
Corrode metals
Electrolytes
React with bases to form a salt and water
pH is less than 7
Turns blue litmus paper to red “Blue to Red A-CID”
Acid Nomenclature Review : Acid Nomenclature Review Binary Ternary An easy way to remember which goes with which…
“In the cafeteria, you ATE something ICky”
Acid Nomenclature Flowchart : Acid Nomenclature Flowchart
Some Properties of Bases : Some Properties of Bases Produce OH- ions in water
Taste bitter, chalky
Are electrolytes
Feel soapy, slippery
React with acids to form salts and water
pH greater than 7
Turns red litmus paper to blue “Basic Blue”
Some Common Bases : Some Common Bases NaOH sodium hydroxide lye
KOH potassium hydroxide liquid soap
Ba(OH)2 barium hydroxide stabilizer for plastics
Mg(OH)2 magnesium hydroxide “MOM” Milk of magnesia
Al(OH)3 aluminum hydroxide Maalox (antacid)
Acid/Base definitions : Acid/Base definitions Definition #1: Arrhenius (traditional)
Acids – produce H+ ions (or hydronium ions H3O+)
Bases – produce OH- ions
(problem: some bases don’t have hydroxide ions!)
Slide 12 : Arrhenius acid is a substance that produces H+ (H3O+) in water Arrhenius base is a substance that produces OH- in water
Acid/Base Definitions : Acid/Base Definitions Definition #2: Brønsted – Lowry
Acids – proton donor
Bases – proton acceptor
A “proton” is really just a hydrogen atom that has lost it’s electron!
Slide 14 : A Brønsted-Lowry acid is a proton donor
A Brønsted-Lowry base is a proton acceptor acid conjugate base base conjugate acid
ACID-BASE THEORIES : ACID-BASE THEORIES The Brønsted definition means NH3 is a BASE in water — and water is itself an ACID
Conjugate Pairs : Conjugate Pairs
Learning Check! : Learning Check! Label the acid, base, conjugate acid, and conjugate base in each reaction: HONORS ONLY! HCl + OH- Cl- + H2O H2O + H2SO4 HSO4- + H3O+
Lewis Acids & Bases : Formation of hydronium ion is also an excellent example. Lewis Acids & Bases Electron pair of the new O-H bond originates on the Lewis base.
Lewis Acid/Base Reaction : Lewis Acid/Base Reaction
The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion.Under 7 = acid 7 = neutralOver 7 = base : The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion.Under 7 = acid 7 = neutralOver 7 = base
pH of Common Substances : pH of Common Substances
pH calculations – Solving for H+ : pH calculations – Solving for H+ If the pH of Coke is 3.12, [H+] = ???
Because pH = - log [H+] then
- pH = log [H+]
Take antilog (10x) of both sides and get
10-pH = [H+]
[H+] = 10-3.12 = 7.6 x 10-4 M
*** to find antilog on your calculator, look for “Shift” or “2nd function” and then the log button
More About Water : More About Water H2O can function as both an ACID and a BASE.
In pure water there can be AUTOIONIZATION Equilibrium constant for water = Kw
Kw = [H3O+] [OH-] = 1.00 x 10-14 at 25 oC HONORS ONLY!
pOH : pOH Since acids and bases are opposites, pH and pOH are opposites!
pOH does not really exist, but it is useful for changing bases to pH.
pOH looks at the perspective of a base
pOH = - log [OH-]
Since pH and pOH are on opposite ends,
pH + pOH = 14
Slide 25 : pH [H+] [OH-] pOH
Slide 26 : HNO3, HCl, H2SO4 and HClO4 are among the only known strong acids. Strong and Weak Acids/Bases The strength of an acid (or base) is determined by the amount of IONIZATION. HONORS ONLY!
Strong and Weak Acids/Bases : Strong and Weak Acids/Bases Generally divide acids and bases into STRONG or WEAK ones.
STRONG ACID: HNO3 (aq) + H2O (l) ---> H3O+ (aq) + NO3- (aq)
HNO3 is about 100% dissociated in water. HONORS ONLY!
Slide 28 : Weak acids are much less than 100% ionized in water.
One of the best known is acetic acid = CH3CO2H Strong and Weak Acids/Bases HONORS ONLY!
Slide 29 : Strong Base: 100% dissociated in water.
NaOH (aq) ---> Na+ (aq) + OH- (aq) Strong and Weak Acids/Bases Other common strong bases include KOH and Ca(OH)2.
CaO (lime) + H2O -->
Ca(OH)2 (slaked lime) HONORS ONLY!
Slide 30 : Weak base: less than 100% ionized in water
One of the best known weak bases is ammonia
NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq) Strong and Weak Acids/Bases HONORS ONLY!
Weak Bases : Weak Bases HONORS ONLY!
Equilibria Involving Weak Acids and Bases : Equilibria Involving Weak Acids and Bases Consider acetic acid, HC2H3O2 (HOAc)
HC2H3O2 + H2O H3O+ + C2H3O2 -
Acid Conj. base (K is designated Ka for ACID)
K gives the ratio of ions (split up) to molecules (don’t split up) HONORS ONLY!
Types of Acid/Base Reactions: Summary : Types of Acid/Base Reactions: Summary HONORS ONLY!
pH testing : 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
Paper testing : 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.
Slide 36 : pH paper
pH meter : pH meter Tests the voltage of the electrolyte
Converts the voltage to pH
Very cheap, accurate
Must be calibrated with a buffer solution
pH indicators : 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