Acids & Bases Properties Acid-Base Theories Acid-Base Reactions

Properties Both conduct electricity (electrolytes) because they break apart to some degree in water. Acids produce H + (proton) in water. Bases produce OH - (hydroxide) in water. Samples: Acids: vinegar(acetic acid), lactic acid in sour milk, citric acid, Bases: ammonia, lye (NaOH), Milk of Magnesia Mg(OH) 2.

More on Acids 1.Sour taste. NEVER taste acids in lab situations. 2.Change color of indicators. 3.Some acids react with metals & release H 2 gas. 4.Acids react with bases to produce salt & water. When neutralization occurs, #1.-#3 disappear. 5.Conduct electric current.

Neutralization Reaction Acid + Base --> Salt + Water HCl + NaOH --> NaCl + H 2 0 H 2 SO 4 + Ca(OH) 2 --> CaSO 4 + 2H 2 0

Acid Nomenclature Binary Acids contain Hydrogen and another element: Hydro + root of 2 nd element + ic – HFhydrofluoric acid – HClhydrochloric acid – HBrhdrobromic acid – HIhydroiodic … – H2Shydrosulfuric …

Oxyacids Contain H, O, and a 3 rd element. More are listed in your book.

Common Industrial Acids Sulfuric Nitric Phosphoric Hydrochloric Acetic

Bases Bitter taste (NEVER taste bases in labs). Change the color of indicators. Slippery feel (dilute bases, don’t touch concentrated bases) React with acids to produce salt & water Conduct electric current.

Arrhenius Acids & Bases Arrhenius Acid is a chemical compound that increases the concentration of hydrogen ions, H+, in aqueous solutions. Arrhenius Base is a chemical compound that increases the concentration of hydroxide ions, OH-, in aqueous solutions. When put with water, these compounds dissociate (break apart) forming ions

HNO 3 (l) + H 2 0 (l) --> NO 3 - (aq) + H (aq) When put in water, HNO 3, ionizes and the charged particles formed can conduct electricity. The amount of H (hydronium) produced is an indication of the acid’s strength.

Strong Acids ionize completely in water. Strong Acids: HI HClO 4 HBr HCl H 2 SO 4 HClO 3 Weak Acide release few hydrogen ions in water. Weak Acids: HSO 4 - H 3 PO 4 HF CH 3 COOH H 2 CO 3 H 2 S HCN HCO 3 -

For Bases, the strength depends on how it dissociates (ionizes) Strong Bases ionize completely. Strong Bases Ca(OH) 2 --> Ca OH - Sr(OH) 2 Ba(OH) 2 NaOH KOH RbOH CsOH Weal Bases ionize slightly. Weak Bases NH 3 + H 2 O NH OH - C 6 H 5 NH 2 “ means the reaction is reversible

Assignment #72: 476/1-4 #75: 491/1,4-11

Acid-Base Theories Bronsted-Lowry Acids donate protons (H + ) Molecules or ions can donate protons. HCl + NH 3  NH Cl -

The HCl is a Bronsted-Lowry Acid. It donates a proton to water Water can act as a Bronsted-Lowry Acid also as in the following reaction: H2O (l) + NH3 OH- + NH4+

Bronsted-Lowry Bases accept protons. In the equation below, ammonia is the base, because it accepts the proton to become an ammonium ion. acid base HCl + NH 3  NH Cl -

Mono- and Polyprotic Acids Monoprotic acids can only donate one proton per molecule. Ex.: HCl, HNO 3 Polyprotic acids can donate 2 or more protons per molecule. Ex.: H 2 SO 4, H 3 PO 4 For polyprotic acids the donations occur in stages, losing one H + at a time.

Lewis Acids and Bases Arrhenius and Bronsted-Lowery definitions have some limitations. Lewis classification is based on bonding and structure including substances without hydrogen. The Lewis classification is more complete than the other 2 methods.

A Lewis acid is an atom, ion or molecule that accepts an electron pair to form a covalent bond. Dot notation Structural formula – a bar represents what? A pair of shared electrons.

A Lewis base is an atom, ion, or molecule that donates an electron pair to form a covalent.

Lewis Acid-Base Reaction is the formation of one or more covalent bonds between an electron-pair donor and an electron-pair acceptor. Pair of donated electrons

Assignment: #73: 482/1,2 #76: 491/12-15,17,18 Samples are done on the next 2 frames.

491/15. Dilute HCl(aq) and KOH(aq) are mixed in chemically equivalent quantities. a)Write the formula equation for the reaction. HCl(aq) + KOH(aq) --> KCl(aq) + H 2 O(l) b)Write the overall ionic equation. H 3 O + (aq) + Cl - (aq) + K + (aq) + OH - (aq) --> K + (aq) + Cl - (aq) + 2H 2 0(l) c) Write the net ionic equation. H 3 O + (aq) + OH - (aq) --> 2H 2 0(l)

492/17a. Write the formula equation and net ionic equation for this reaction. Formula equation for: Zn(s) + HCl(aq) --> Zn(s) + 2HCl(aq) --> ZnCl 2 (aq) + H 2 (g) Overall ionic equation: Zn(s) + 2H 3 O + (aq) + 2Cl - (aq) --> Zn 2+ (aq) + 2Cl - (aq) + H 2 (g) + 2H 2 0(l) Net ionic equation: Zn(s) + 2H (aq) --> Zn 2+ (aq) + H 2 (g) + 2H 2 0(l)

Acid-Base Reactions Now we are going to use Bronsted-Lowry description to explore acid-base reactions. What was the Bronsted-Lowery theory? B-L acid donates protons B-L base accepts protons

A conjugate base is the species that remains after a Bronsted-Lowery acid has given up a proton. A conjugate acid is the species that forms when a Bronsted-Lowery base gains a proton.

Acid-Base Reactions Now we are going to use Bronsted-Lowry definitions to study Acid-Base reactions. The species that remains after a Bronsted-Lowry acid has given up a proton is the conjugate base of that acid. HF + H 2 O F - + H Acid conjugate base

The species that is formed when a Bronsted- Lowry base gains a proton is the conjugate acid of that base. HF(aq) + H 2 O(l) F - (aq) + H (aq) Base conjugate acid

HF(aq) + H 2 O(l) F - (aq) + H (aq) Acid Base conjugate conjugate base acid acid 1 base 2 base 1 acid 2 Conjugate pairs: (1)HF and F - (2)H 2 0 and H 3 0 +

Strength of Conjugate Acids & Bases On Page 1 of your handout for this chapter, you have a table which lists and compares the strengths of various acids and their conjugate bases. Get your Ch. 14 handout out now.

Determining direction of equilibrium in Acid-Base reactions The stronger an acid is, the weaker its conjugate base will be. The stronger a base is, the weaker its conjugate acid will be. From these concepts, we can predict the outcome of a reaction.

Assignment for this section: #74: 489/1,2 #77: 491/19-25 #78: 492/26-30,36,37 (Overall practice problems) Sample problem on next page:

492/23a: Identify the proton donor or acid and the proton acceptor or base. Label each acid- base conjugate pair. CH 3 COOH + H 2 0 H CH 3 COO - acid base conjugate conjugate acid base

Another sample. 492/29a. Write the formula equation, the overall ionic equation, and the net ionic equation for a neutralization reaction that would form RbClO 4. Formula equation: RbOH(aq) + HClO 4 (aq) --> RbClO 4 (aq) + H 2 0(l)

Overall Ionic equation: Rb + (aq) + OH - (aq) + H (aq) + ClO 4 - (aq) --> Rb + (aq) + ClO 4 - (aq) + 2H 2 0(l) Net ionic equation: H (aq) + OH - (aq) --> 2H 2 0(l)

Amphoteric Compounds These can act as either an acid or a base. Water acts as a base in this reaction: H 2 SO 4 (aq) + H 2 0(l) --> H (aq) + HSO 4 - (aq) acid 1 base 2 acid 2 base 1 But, water acts as an acid here: NH 3 (g) + H 2 0(l) NH 4 + (aq) + OH - (aq) Base 1 acid 2 acid 1 base 2

Review AcidsBases Arrhenius concentration of: [H + ] [OH - ] Bronsted-Lowry H + donor H + acceptor Lewis, electron pair: acceptor donor