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Acid and Base Definitions 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")!
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 þ Produce H + (as H 3 O + ) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) þ Taste sour þ Corrode metals þ Electrolytes þ React with bases to form a salt and water þ pH is less than 7 þ Turns blue litmus paper to red “Blue to Red A-CID”
Acid Nomenclature Review No Oxygen w/Oxygen An easy way to remember which goes with which… “In the cafeteria, you ATE something ICky”
HBr (aq)HBr (aq) H 2 CO 3H 2 CO 3 H 2 SO 3H 2 SO 3 hydrobromic acid carbonic acid sulfurous acid Acid Nomenclature Review
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 NaOHsodium hydroxidelye KOHpotassium hydroxideliquid soap Ba(OH) 2 barium hydroxidestabilizer for plastics Mg(OH) 2 magnesium hydroxide“MOM” Milk of magnesia Al(OH) 3 aluminum hydroxideMaalox (antacid) Al(OH) 3 aluminum hydroxideMaalox (antacid)
Acid/Base definitions Definition #1: Arrhenius (traditional) Acids – produce H + ions (or hydronium ions H 3 O + ) in water Bases – produce OH - ions in water (problem: some bases don’t have hydroxide ions!)
Arrhenius acid is a substance that produces H + (H 3 O + ) in water Arrhenius base is a substance that produces OH - in water
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!
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 The Brønsted definition means NH 3 is a BASE in water — and water is itself an ACID
Amphoteric Substances A substance that is amphoteric can act as either an acid or a base. In the previous slide, water acted as an acid. In the following example, water acts as a base. HCl (g) + H 2 O (l) H 3 O + (aq) + Cl - (aq) acid base conj. acid conj. base
Acid-Base Behavior Consider a compound having the formula HOX. If X is highly electronegative, it will have a strong attraction for the electrons shared with O. – The O, will in turn, pull strongly on the electrons held shared with H. – This H will then be easily lost = acid If X has a low electronegativity, the oxygen will pull the electrons away from X. – The hydrogen will remain joined to the oxygen. – Since the O and H can easily remain together, it is likely that OH - will be formed = base Nonmetals tend to have high EN = acids Metals tend to have low EN = bases
Acids & Base Definitions Lewis acid - a substance that accepts an electron pair Lewis base - a substance that donates an electron pair Definition #3 – Lewis
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.Electron pair of the new O-H bond originates on the Lewis base.
Lewis Acid-Base Interactions in Biology The heme group in hemoglobin can interact with O 2 and CO. The heme group in hemoglobin can interact with O 2 and CO. The Fe ion in hemoglobin is a Lewis acid The Fe ion in hemoglobin is a Lewis acid O 2 and CO can act as Lewis bases O 2 and CO can act as Lewis bases Heme group
HOMEWORK 1)Identify the acid, base, conjugate acid, and conjugate base in the following reactions (using the Bronsted-Lowry definition): a)HNO 3 (aq) + NaOH (aq) H 2 O (l) + NaNO 3 (aq) b)NaHCO 3 (aq) + HCl (aq) NaCl (aq) + H 2 CO 3 (aq) 2)What is the conjugate base of each of the following acids? a)H 2 SO 3 c) NH 3 b)H 2 CO 3 d) HF 3) Classify each of the following substances as either a Lewis acid or a Lewis base: a)Cl - c) Na + b)CO 3 2- d) Br -
MORE HOMEWORK 4)Describe the differences in the three acid- base definitions of this PowerPoint. 5)What are conjugate acids and bases? 6)Name the following substances: a)HCl (aq)b) H 2 SO 4 c) KOH 7)What kind of element would you expect to find in position X of the compound HOX if the compound is determined to be amphoteric?