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Acids and Bases.

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Presentation on theme: "Acids and Bases."— Presentation transcript:

1 Acids and Bases

2 Properties of Acids Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) Taste sour Corrode metals Good Electrolytes React with bases to form a salt and water pH is less than 7 Turns blue litmus paper to red “Blue to Red A-CID”

3 Properties of Bases Generally produce OH- ions in water
Taste bitter, chalky Are electrolytes Feel soapy, slippery React with acids to form salts and water pH greater than 7 Turns red litmus paper to blue “Basic Blue”

4 Naming Acids Binary Acid – An acid that contains only two elements, one of which is hydrogen and one which is more electronegative. HF – Hydrofluoric acid HCl – Hydrochloric acid Oxyacid – An acid that has hydrogen, oxygen, and a third element that is usually a non-metal HClO4 – Perchloric acid HNO2 – Nitrous acid H2CO3 – Carbonic acid

5 Arrhenius Definition Acid - Substances in water that increase the concentration of hydrogen ions (H+). Base - Substances in water that increase concentration of hydroxide ions (OH-). Problem – many bases do not actually contain hydroxides

6 Bronsted-Lowry Definition
Acid - neutral molecule, anion, or cation that donates a proton. Base - neutral molecule, anion, or cation that accepts a proton. HA + :B  HB :A- HCl + H2O  H3O Cl- Acid Base Conj Acid Conj Base

7 Conjugate Acid Base Pairs
Conjugate Base - The species remaining after an acid has transferred its proton. Conjugate Acid - The species produced after base has accepted a proton. HA & :A- - conjugate acid/base pair :A- - conjugate base of acid HA :B & HB+ - conjugate acid/base pair HB+ - conjugate acid of base :B

8 Examples of Bronsted-Lowry Acid Base Systems
Note: Water can act as acid or base Acid Base Conjugate Acid Conjugate Base HCl + H2O  H3O Cl- H2PO4- + H2O  H3O HPO42- NH4+ + H2O  H3O NH3 Base Acid Conjugate Acid Conjugate Base :NH H2O  NH OH- PO H2O  HPO OH-

9 Diprotic and Triprotic Acids (Polyprotic)
Sulfuric Acid can donate two protons per molecule Phosphoric acid can donate three protons per molecule H3PO4 + H2O  H3O+ + H2PO4- H2PO4- +H2O  H3O+ + HPO42- HPO42- +H2O  H3O+ + PO43-

10 G.N. Lewis Definition Lewis Acid - an electron pair acceptor
Base - an electron pair donor

11 Common Strong Acids/Bases
Hydrochloric Acid Nitric Acid Sulfuric Acid Perchloric Acid Strong Bases Sodium Hydroxide Potassium Hydroxide *Barium Hydroxide *Calcium Hydroxide *While strong bases they are not very soluble

12 Acid Strength Strong Acid Weak Acid
Transfers all of its protons to water Transfers only a small fraction of its protons to water Completely Ionized Partly Ionized Strong Electrolyte Weak Electrolyte Conjugate Base is Weaker Conjugate Base is Stronger As acid strength decreases, base strength increases The stronger the acid, the weaker its conjugate base The weaker the acid, the stronger its conjugate base

13 Base Strength Strong Base Weak Base All molecules accept a proton
Fraction of molecules accept a proton Completely Ionized Partly Ionized Strong Electrolyte Weak Electrolyte Conjugate Acid is Weaker Conjugate Acid is Stronger As base strength decreases, acid strength increases The stronger the base, the weaker its conjugate acid The weaker the base, the stronger its conjugate acid

14 Salts & Neutralization
A salt is the neutralization product of an acid and a base. The anion comes from the acid and the cation from the base. Examples HCl NaOH  NaCl + H2O. H2SO4 + 2 KOH  K2SO4 + H2O.

15 The pH Scale pH [H3O+ ] [OH- ] pOH

16 pH and acidity Acidity or Acid Strength depends on Hydronium Ion Concentration [H3O+] The pH system is a logarithmic representation of the Hydrogen Ion concentration (or OH-) as a means of avoiding using large numbers and powers. pH = - log [H3O+] pOH = - log [OH-] 3. What is the pH of a solution if the [H3O+] is 3.4 x 10-5 M? pH = -log [H3O+] = -log(3.4 x 10-5) = 4.47

17 pH and acidity Kw = [H3O+] [OH-] = 1.0 x10-14 In pure water
pH + pOH = 14

18 Indicators

19 pH and acidity The pH values of several common substances are shown at the right. Many common foods are weak acids Some medicines and many household cleaners are bases.

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