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1 Acids and Bases. 2 Properties of Acids þ Produce H + (as H 3 O + ) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule)

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Presentation on theme: "1 Acids and Bases. 2 Properties of Acids þ Produce H + (as H 3 O + ) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule)"— Presentation transcript:

1 1 Acids and Bases

2 2 Properties of Acids þ Produce H + (as H 3 O + ) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) þ Taste sour þ Corrode metals þ Good Electrolytes þ React with bases to form a salt and water þ pH is less than 7 þ Turns blue litmus paper to red “Blue to Red A-CID”

3 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 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 HClO 4 – Perchloric acid HNO 2 – Nitrous acid H2CO 3 – Carbonic acid

5 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 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 + H 2 O  H 3 O + + Cl - Acid Base Conj Acid Conj Base

7 7 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 Conjugate Acid Base Pairs

8 8 Note: Water can act as acid or base AcidBase Conjugate Acid Conjugate Base HCl+ H 2 O  H 3 O + +Cl - H 2 PO H 2 O   H 3 O + + HPO 4 2- NH H 2 O   H 3 O + +NH 3 BaseAcid Conjugate Acid Conjugate Base :NH 3 + H 2 O   NH 4 + +OH - PO H 2 O   HPO OH - Examples of Bronsted- Lowry Acid Base Systems

9 9 Diprotic and Triprotic Acids (Polyprotic) Sulfuric Acid can donate two protons per molecule Phosphoric acid can donate three protons per molecule H 3 PO 4 + H 2 O   H 3 O + + H 2 PO 4 - H 2 PO 4 - +H 2 O   H 3 O + + HPO 4 2- HPO H 2 O   H 3 O + + PO 4 3-

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

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

12 12 Acid Strength Strong AcidWeak Acid Transfers all of its protons to water Transfers only a small fraction of its protons to water Completely IonizedPartly Ionized Strong ElectrolyteWeak Electrolyte Conjugate Base is WeakerConjugate 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 13 Base Strength Strong BaseWeak Base All molecules accept a proton Fraction of molecules accept a proton Completely IonizedPartly Ionized Strong ElectrolyteWeak Electrolyte Conjugate Acid is WeakerConjugate 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 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 + H 2 O. H 2 SO KOH  K 2 SO 4 + H 2 O.

15 15 The pH Scale pH [H 3 O + ] [OH- ] pOH

16 16 pH and acidity 1.Acidity or Acid Strength depends on Hydronium Ion Concentration [H 3 O + ] 2.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 [H 3 O + ] pOH = - log [OH - ] 3. What is the pH of a solution if the [H 3 O + ] is 3.4 x M? pH = -log [H 3 O + ] = -log(3.4 x ) = 4.47

17 17 pH and acidity Kw = [H 3 O + ] [OH - ] = 1.0 x In pure water [H 3 O + ] = [OH - ] = 1.0 x10 -7 pH + pOH = 14

18 18 Indicators

19 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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