Unit 12: Acids, Bases, and Salts

Properties of Acids Taste sour Electrolytes: substances that produce ions in solution and as a result conduct electricity Strong acid  strong electrolyte Weak acid  weak electrolyte Will react with active metals (above H2 on Table J) to produce H2(g)

Review of Naming Rules Binary Acids: hydro_______ic acid Ternary Acids (use Table E) ate ic ite ous

Properties of Bases Taste bitter Turn litmus paper blue Feel slippery (ex. soap) Strong bases consist of a Group 1 or Group 2 metal w/ hydroxide ion

Look in RT for common acids and bases

Electrolytes Form ions in water Conduct electricity Salts Ionic Compounds M to NM Acids pH < 7 H+ > OH- Bases pH > 7 OH- > H+ Molecules (NM to NM) are NOT electrolytes…do NOT produce ions in solution!!

Indicators- Table M Below the range  the color is given on the left Above the range  the color is given on the right. Acids: Turn litmus red and phth colorless Bases: Turn litmus blue and phth pink.

Universal Indicator

Arrhenius Theory of Acids and Bases Arrhenius Acid Arrhenius Base A substance, that when dissolved in water, produces H+ ions as the only positive ions in solution A substance, that when dissolved in water, produces OH- ions as the only negative ions in solution Monoprotic, diprotic, triprotic Hydronium ion HCl (aq)  H+ (aq)+ Cl- (aq) NaOH (aq)  Na+ (aq) + OH- (aq) hydrogen ion, same as H3O+ (hydronium ion) hydroxide ion

Bronsted-Lowry Theory of Acids and Bases ***based on the proton (H+) Bronsted Acid Bronsted Base A proton donor A proton acceptor Must release the H+ (aq) ion Does not need to have the OH-(aq) ion, but MUST have a lone pair of electrons. Ex) HCl (aq) Ex) NH3 (aq)

Reversible Acid-Base Rxns Acid-Base reactions can be reversible! H2SO4(aq) + NH3(aq) HSO4-(aq) + NH4+(aq) B.A. B.B. B.B. B.A. A conjugate acid-base pair consists of two substances related by the loss or gain of a single hydrogen ion (H+) Pg.9

Amphoteric Substances A substance that can act as both an acid and a base is said to be amphoteric Ex) HCO3- (aq) + H2O (l)  CO32- (aq) + H3O+(aq) **Here, HCO3- acts as an acid Ex) HCO3- (aq) + H2O (l)  H2CO3 (aq) + OH- (aq) **Here, HCO3- acts as a base Water is a common amphoteric substance- can act as both an acid and base

Water as an Acid/Base Water molecules undergo self-ionization H2O(l) + H2O (l) H3O+ (aq) + OH- (aq) In pure water, the equilibrium concentration of [H3O+] = [OH-] = 1 x 10-7 M In other words, a neutral solution has the same number of moles of H+ ions as OH- ions.

“See-Saw Diagram” Ion-Product Constant for Water (for aqueous solutions) Kw= [H+] x [OH-] = 1.0 x 10-14 ** exponents always add to 14

The pH scale Scale is based on the concentration of H+ ions in aqueous solution pH = - log [H+] pH < 7, acidic pH = 7, neutral pH > 7, basic

Determining pH given concentrations [H+] = 1.0 x 10-6 M pH = 6 pH + pOH ALWAYS equals 14 [OH-] = 1.0 x 10-8 M pOH = 8

The pH scale is logarithmic An increase in one unit of the pH scale represents a ten-fold decrease (x 10) in the H+ ion concentration

Practice pH 6 to pH 4 pH 5 to pH 6 [H+] increases by a factor of 100 [H+] decreases by a factor of 10 pH 2 to pH 4 [H+] decreases by factor of 100

Neutralization Reactions Neutralization occurs when an acid and a base react to form a salt and water Acid + Base  salt + water HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l) Acid Base Salt Water

Titrations Used to determine the concentration of an acid or base The equivalence point is reached when the moles H+ = moles OH- Titration Equation: MaVa = MbVb ** Can use any unit of volume as long as you are consistent

unknown volume, known concentration Known volume, unknown concentration

Warm-Up In the lab, a student neutralized 1.5 M nitric acid with 0.50 M magnesium hydroxide. Write the balanced equation for the rxn between the acid and base given above. How many mL of 0.50 magnesium hydroxide are needed to neutralize 10.0 mL of 1.5 M nitric acid?

Indicators for Titrations Phenolphthalein is used to approximate the endpoint of a titration. Colorless indicates an acidic solution and pink indicates a basic solution When a pale pink color persists, the endpoint has been reached The endpoint, or equivalence point, is when moles H+ = moles OH- (pH =7)

Indicators- Table M Below the range  the color is given on the left Above the range  the color is given on the right.

Strength of Acids/Bases Strong Acids: Strong Bases: HCl HBr HI HClO4 H2SO4 HNO3 Any Group 1 or 2 metal bonded to an OH- ion Consider everything else to be weak!

Chemistry of Dyeing Eggs https://www.youtube.com/watch?v=lMQ_qhEe yl8