1. Acids and Bases Mr. Sonaji V. Gayakwad Asst. professor
Dept of chemistry
Mrs.K.S.K. College,Beed

2. Arrhenius theory of Acid and Bases Arrhenius Acids
Hydrogen-containing compounds that ionize to yield hydrogen ions (H+) in aqueous solutions
Arrhenius Bases
Compounds that ionize to yield hydroxide ions (OH- ) in aqueous solutions

3. Bronsted-Lowry theory of Acids and bases
Bronsted-Lowry Acid
A hydrogen-ion donor
Bronsted-Lowry Base
A hydrogen-ion acceptor

4. All acids and bases in the Arrhenius theory are also acids and bases based on Bronsted- Lowry theory.
Bronsted-Lowry includes some bases not included in the Arrhenius theory.
Ex: Ammonia (NH3)

5. Lewis concept of Acids and Bases: Lewis Acid
Substance that can accept a pair of electrons to form a covalent bond
Lewis Base
Substance that can donate a pair of electrons to form a covalent bond

6. What are acids and bases?
Summary of Acid-Base Definitions
Theory
Acid
Base
Arrhenius
H+ producer
OH- producer
Bronsted-Lowry
H+ donor
H+ acceptor
Lewis
Electron-pair acceptor
Electron-pair donor

7. Strengths of Acids and Bases:
Strong acids – completely ionised in aqueous solution
Ex: HCl; HNO3; H2SO4
Weak acids – ionise only slightly in aqueous solution
Ex: Acetic acid – 1% of acetic acid molecules ionised at any instant

8. Strong bases – dissociate completely into metal ions and hydroxide ions in aqueous solution
Ex: Ca(OH)2; NaOH; KOH
Weak bases – react with water to form hydroxide ion and the conjugate acid of the base (No OH in formula)
Ex: CH3NH2, NH3

9. Single Element: Polyatomic Ion: Hydro_____ic acid
Ex: HCl = Hydrochloric acid
Polyatomic Ion:
ATEic ITEous
Ex: H2SO4 = sulfuric acid
Ex: H2SO3 = sulfurous acid

10. Bases are named the same way as any other ionic compound
Ex: KOH = potassium hydroxide

11. Water that LOSES a hydrogen ion becomes a negatively charged hydroxide ion (OH-)
Water that GAINS a hydrogen ion becomes a positively charged hydronium ion (H3O+)

12. Self-ionisation of water: reaction in which TWO water molecules produce ions
Ex: H2O + H2O  H3O+ + OH-
Can also be written as a DISSOCIATION:
Ex: H2O (l)  H+ (aq) + OH- (aq)

13. In water or aqueous solution, hydrogen ions (H+) are joined to water molecules to form hydronium ions (H3O+)
H+ and H3O+ are both used to represent hydrogen ions in aqueous solution

14. Acidity or basicity of a solution is discussed in terms of the concentration of hydrogen ions, [H+], or the concentration of hydroxide ions, [OH-]
Acidic: [H+] > [OH-]
Basic (Alkaline): [H+] < [OH-]
Neutral: [H+] = [OH-]

15. Acidity is measured in pH
pH = -log[H+]
Acidic: pH < 7; [H+] > 1 x 10-7 M
Basic: pH > 7; [H+] < 1 x 10-7 M
Neutral: pH = 7; [H+] = 1 x 10-7 M

16. Basicity could be measured in a similar manner called pOH
pOH = -log[OH-]
pH + pOH = 14

17. Acid-Base Indicators pH Meters
An indicator’s acid and base form have different colors in solution
Limitations: usually work at 25°C
pH Meters
Ex: PASCO Probes
Make rapid, accurate pH measurements
Must be calibrated – put into solution of known pH

18. Neutralisation reaction: hydronium ions combine with hydroxide ions to form water
An indicator can be used to show when the neutralisation is complete