PROPERTIES OF ACIDS & BASES

WHAT IS AN ACID? A compound that donates a hydrogen ion (H+) when dissociated

ACID PROPERTIES aqueous solutions have a sour taste change the color of acid-base indicators when reacted with an active metal, releases hydrogen gas Zn (s) + H2SO4 (aq)  ZnSO4 (aq) + H2 (g)

ACID PROPERTIES when reacted with base, produces salt and water HCl (aq) + NaOH (aq)  NaCl (s) + H2O (l) conduct electric current Turns litmus paper red

STRONG VS. WEAK ACIDS Strong acids dissociate completely Every H+ ion breaks off Weak acids dissociate incompletely A few H+ ions break off then reform

WHAT IS A BASE? A compound that accepts a hydrogen ion (H+) OR contains OH- ion

BASE PROPERTIES aqueous solutions of bases have a bitter taste bases change the color of acid base indicators dilute aqueous solutions of bases feel slippery

BASE PROPERTIES when reacted with acid, produces salt and water conduct electric current Turns litmus paper blue

Learning Check Describe the solution in each of the following as: 1) acid 2) base or 3)neutral A. soda B. soap C. coffee D. wine E. water F. grapefruit

Relationship of [H3O+] and [OH-] Section 1 What Are Acids and Bases? Chapter 15 Relationship of [H3O+] and [OH-]

DIFFERENT DEFINITIONS SHOULD BE MEMORIZED

ARRHENIUS ACID A chemical compound that increases the concentration of H+ ions in solution Good for calculating pH BASE A chemical compound that increases the concentration of OH- ions in solution Good for calculation pOH Limited to bases containing OH-

HCl  H+(aq) + Cl-(aq) Arrhenius Definition NaOH  Na+(aq) + OH-(aq) In aqueous solution… Acids form hydrogen ions (H+) water HCl  H+(aq) + Cl-(aq) In aqueous solution… Bases form hydroxide ions (OH-) water NaOH  Na+(aq) + OH-(aq)

Brønsted-Lowry Classification, continued Section 1 What Are Acids and Bases? Chapter 15 Brønsted-Lowry Classification, continued Brønsted-Lowry Acids Donate Protons, continued

BRONSTED-LOWRY ACID A molecule or ion that is a proton (H+) donor BASE A molecule or ion that is a proton (H+) acceptor Includes compounds w/o OH-

HCl + H2O  Cl– + H3O+ acid conjugate base base conjugate acid Brønsted-Lowry Acids are proton (H+) donors Bases are proton (H+) acceptors HCl + H2O  Cl– + H3O+ acid conjugate base base conjugate acid

HCl + H2O  Cl– + H3O+ acid conjugate base base conjugate acid

Acids and bases come in pairs... A conjugate base is the remainder of the original acid, after it donates it’s hydrogen ion A conjugate acid is the particle formed when the original base gains a hydrogen ion General equation is: HA(aq) + H2O(l) H3O+(aq) + A-(aq) Acid Base Conj acid Conj base

Examples 1.HCl + NH3 
NH4+ + Cl– 2.OH– + HCN
 H2O + CN– 3. PO43– + HNO3 
NO3– + HPO42- 4.HCO3– + HCl 
H2CO3 + Cl–

Why don’t we like this definition? LEWIS ACID Electron pair acceptor BASE Electron pair donator Why don’t we like this definition?

HCl(aq) + H2O(l)  H3O+(aq) + Cl–(aq) Hydronium Ion H3O+ Often the term H+ for convenience, it is more accurate to use H3O+ HCl(aq) + H2O(l)  H3O+(aq) + Cl–(aq) H Cl O – +

Amphoteric - can be an acid or a base Ex.1- Water as a base Amphoteric - can be an acid or a base (ex. water) H2O + HNO3  H3O+ + NO3– B A CA CB

Ex. 2- Water as an acid NH3 + H2O  NH4+ + OH- B A CA CB

Acid-Base Titrations and pH

pH pH < 7 is acidic pH = 7 is neutral pH > 7 is basic

[H+] = concentration in molarity Calculating pH pH = - log [H+] pH = power of Hydrogen [H+] = concentration in molarity

Calculating pOH pOH = - log [OH-] pOH = power of Hydroxide [OH-] = concentration in molarity pH + pOH = 14

CALCULATING pH FROM CONCENTRATION SAMPLE PROBLEM A What is the pH of a 1 x 10-3 M HCl solution?

SAMPLE PROBLEM B What is the pH of a 2.5 x 10-2 M H2SO4 solution?

SAMPLE PROBLEM C What is the pH of a 2.5 x 10-2 M NaOH solution?

[H3O+] CALCULATING CONCENTRATION FROM pH [H3O+] = 10-pH [H3O+] = concentration of acid (N) Look for your log button. Above it – 10x To access it, hit 2nd F key Hit log key

[OH-] = concentration of base (M) [OH-] = 10-pOH [OH-] = concentration of base (M) [H3O+] [OH-] = 1.0 x 10-14

SAMPLE PROBLEM D What is the concentration of a HCl solution with pH of 5.6?

SAMPLE PROBLEM E What is the concentration of a Mg(OH)2 solution with pH of 5.6?

NEUTRALIZATION REACTIONS

NEUTRALIZATION REACTIONS The reaction of an acid and a base to form salt & water H+ ions react with OH- to form water Predict products as in a double replacement rxn (partner swap) HCl (aq) + NaOH (aq)  H2O (l) + NaCl (s)

PRACTICE REACTIONS HCl + LiOH  HNO3 + Ca(OH)2  H2SO4 + Al(OH)3 

PRACTICE REACTIONS HCl + LiOH  H2O + LiCl 2 HNO3 + Ca(OH)2  2 H2O + Ca(NO3)2 3 H2SO4 + 2 Al(OH)3  6 H2O + Al2(SO4)3

TITRATIONS MA VA = MB VB

NORMALITY & NEUTRALIZATION REACTIONS MA VA = MB VB Where: MA = molarity of acid VA = volume of acid MB = molarity of base VB = volume of base

NORMALITY & NEUTRALIZATION REACTIONS What volume of a 0.25 M HCl solution is needed to neutralize 36 mL of 0.30 Mg(OH)2 M? Step 1: Start with what you know. NA = (0.25 M) (1) = 0.25 N VA = X mL NB = (0.30 M) (2) = 0.60 N VB = 36 mL