CHAPTER 19 ACIDS & BASES

What do you see?

Acid Properties Sour taste (citrus fruits) Conduct electric current Change the color of indicators-turns litmus paper red pH concentration < 7 React with bases to produce salt and water: HCl + NaOH  H2O + NaCl Some react with metals to release H2 gas: Mg + HCl  MgCl2 + H2

Naming Acids Binary Acids: a. H2S hydrosulfuric acid 2. Ternary Acids: a. H2SO4 - “IC I ATE that” sulfuric acid b. H2SO3 -“RITEOUS” sulfurous acid

Base (alkaline) Properties Bitter taste (coffee) Feel slippery (soap) Change the color of indicators-turns litmus paper blue Caustic- attack the skin, cause severe burns Conduct electric current

Arrhenius Acids and Bases A compound that produces H+ in solution. Ionizes to yield a proton in an aqueous solution. Ex: HCl (g) -------- H+ (aq) + Cl- (aq) Arrhenius Base: A compound that produces OH- in solution. Ex: NaOH (s) --------- Na+ (aq) + OH- (aq) H2O H2O

Hydronium ion The particle formed by the combination of a hydrogen ion with a water molecule. H+ + H2O H3O+1

pH Scale A more convenient way to express acidity pH = -log[H3O+] pOH = -log[OH-] pH + pOH = 14.0

Find the pH and pOH of a 1x10-10 M solution of HBr. 1. HBr is an acid so we are looking at the [H+] concentration. [H+] = 1x10-10 M 2. pH = -log[1x10-10] pH = 10 3. pH + pOH = 14 10 + pOH = 14 pOH = 4

pH pH 0-7: acidic solution pH 7: neutral solution pH 7-14: basic solution

Calculating pH pH = -log [H+] Ex: A solution has a H+ concentration of 1x10-5 pH = -log [1x10-5] pH = 5 and we have an acidic solution Ex: A solution has a pH=8 8 = -log [H+] [H+] = 1 x 10-8

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ACIDS & BASES Titrations CHAPTERS 19 ACIDS & BASES Titrations

Indicators and Titration Acid-Base Indicators: Compounds whose colors are sensitive to pH. Titration: Method used to determine an unknown concentration of solution.

Equivalence Point When the number of moles of hydrogen ions equals the number of moles of hydroxide ions.

NEUTRALIZATION OF ACIDS & BASES If we need to neutralize an acid or a base, we use the following formula: MaVaCb = MbVbCa Mx=Molarity (mol/L) of the acid or base Vx=Volume (L) of the acid or base Cx =Coefficient (balanced eq.) of the acid or base

MaVaCb = MbVbCa Example: A 25mL solution of H2SO4 is neutralized by 18mL of a 1.0M NaOH using phenolphthalein as an indicator. What is the concentration (M) of the H2SO4? Step 1: Write the neutralization rxn and balance H2SO4 + 2NaOH Na2SO4 + 2H2O Step 2: Solve for the unknown. Ma = MbVbCa (1.0M)(0.018L)(1) VaCb (0.025L)(2) Ma = 0.36M

MOLARITY vs NORMALITY Molarity—moles of solute contained in 1 liter of solution (moles/Liter) Normality—moles of reactive units for each liter of solution IN ACID-BASE REACTIONS: CaVa = CbVb Ex #1—H3PO4 (N=H+ ions so N=3) Ex #2---Mg(OH)2 (N=OH- ions so N=2)