Acids & Bases

Properties ACIDS BASES electrolytes  electrolytes sour taste bitter taste turn litmus red turn litmus blue react with metals to form H2 gas slippery feel vinegar, soda, apples, citrus fruits ammonia, lye, antacid, baking soda

Acid and Bases

Acid and Bases

Svante Arrhenius (1859-1927)

HCl + H2O  H3O+ + Cl– Arrhenius Acids – + Arrhenius - In aqueous solution… Acids form hydrogen ions (H+) [hydronium ions (H3O+)] HCl + H2O  H3O+ + Cl– H Cl O – + hydrogen ions (H+) = [hydronium ions (H3O+)] = also called a proton acid

Acids -- Example Hydrochloric Acid Forms Hydrogen Ions (H+) in solution Forms Chloride ions (Cl-) in solution/ water hydrogen ions (H+) = [hydronium ions (H3O+)] = proton

Polyprotic - an acid with more than one H+ Acids Polyprotic - an acid with more than one H+ Monoprotic acids Diprotic acids Triprotic acids H3PO4 HCl H2SO4 HC2H3O2 H2CO3 HNO3

NaOH + H2O  Na+ + OH- Arrhenius Bases Arrhenius - In aqueous solution… Bases form hydroxide ions (OH-) NaOH + H2O  Na+ + OH-

NaOH + H2O  Na+ + OH-

Some Common Bases KOH potassium hydroxide liquid soap NaOH sodium hydroxide lye KOH potassium hydroxide liquid soap Ba(OH)2 barium hydroxide stabilizer for plastics Mg(OH)2 magnesium hydroxide “MOM” Milk of magnesia Al(OH)3 aluminum hydroxide Maalox (antacid)

Copyright Pearson Prentice Hall Acids, Bases, and pH The pH scale  Chemists devised a measurement system called the pH scale to indicate the concentration of H+ ions in solution. The pH scale ranges from 0 to 14. Copyright Pearson Prentice Hall

pH of Common Substances pH Scale pH of Common Substances

pouvoir hydrogène (Fr.) pH Scale 14 7 INCREASING ACIDITY INCREASING BASICITY NEUTRAL pH = -log[H+] pouvoir hydrogène (Fr.) “hydrogen power”

pH Scale = Concentration of H+/ hydrogen ions pH = -log[H+] Power of hydrogen Concentration Of hydrogen ion (H+) Concentration is the amount of a substance (e.g. H+) per unit volume

pH Scale What is the pH of HNO3 with a [H+] concentration of 0.050 M ? pH = -log[H+] pH = -log[0.050] pH = 1.3 Acidic or basic? Acidic

Strong vs. Weak Acids Strong Acids: ionize completely in aqueous solutions Hydrochloric acid (HCl) Nitric acid (HNO3) Sulfuric acid (H2SO4) Weak Acids: ionize only slightly in aqueous solutions Acetic acid (HC2H3O2)

Strong vs. Weak Acids

Strong vs. Weak Acid Protons are hydrogen ions (H+) Negative ions– Non-metal anion

Strong vs. Weak Acid HA H+ + A-   H+ = hydrogen ion A- = any acid anion HA H+ + A- H2O  

Strong vs. Weak Acids H+ = hydrogen ion A- = any acid anion

Strong vs. Weak Bases Strong Bases: ionize completely into metal cations and hydroxide ions Sodium Hydroxide (NaOH) Calcium Hydroxide (Ca(OH)2) Magnesium Hydroxide (Mg(OH)2) Weak Bases: react with water to form hydroxide ions Ammonia (NH3) Not very soluble

Strong Bases Strong Bases will completely ionize (break into ions) in water. Sodium ion (Na+) Hydroxide ion (OH-)

Weak bases Weak bases only partial ionize in water For example, only some ammonia (NH3) becomes ammonium ion (NH4+) and only some water (H20) become hydroxide ion (OH-)

Concentration vs. Strength Concentrated/Dilute = indicate how much of an acid or base is dissolved in solution Strong/Weak = indicates how many molecules ionizes or dissociates Is it possible to have a strong base that is only mildly basic? How?

Concentrated vs. Dilute

Concentrated vs. Dilute