Acids, Bases, and Salts

1. Acids, Bases, and Salts

2. Properties of acids • Taste sour (don’t try this at home). • Conduct electricity. • Some are strong, others are weak electrolytes. • React with metals to form hydrogen gas. • Change indicators (blue litmus to red). • React with hydroxides to form water and a salt.

3. Properties of bases • React with acids to form water and a salt. • Taste bitter. • Feel slippery (don’t try this either). • Can be strong or weak electrolytes. (Strong acid or base strong electrolytes.) (red litmus turns blue).

4. Strong Acid and Bases • STRONG ACIDS AND BASES IONIZE COMPLETELY IN WATER • WEAK ACIDS AND BASES DO NOT IONIZE COMPLETELY IN WATER

5. Measuring pH • pH stands for percentage of hydronium (hydrogen) ions • pH tells us if a solution is acidic or basic • We use a pH scale to determine acidity • 1-6 is acidic • 8-14 is basic • 7 is neutral

7. Acid Base Theories

8. 1. Arrhenius Definition • Acids produce hydrogen ions (H1+) in aqueous solution. • Bases produce hydroxide ions (OH1-) when dissolved in water. • Limited to aqueous solutions. • Only one kind of base (hydroxides) • NH3 (ammonia) could not be an Arrhenius base.

9. #2 Bronsted-Lowry • Acid – donates proton/H+ • Base – accepts proton/H+ • Conjugate base – what is left over after an acid gets rid of a H • Conjugate acid – product that gains the H from the original acid

10. Acids and bases come in pairs... • General equation is: • HA(aq) + H2O(l) H3O+(aq) + A-(aq) • Acid + Base Conjugate acid + Conjugate base • NH3 + H2O NH41+ + OH1- base acid c.a. c.b. • HCl + H2O H3O1++ Cl1- • acid base c.a. c.b. • Amphoteric - acts as acid or base

11. 3. Lewis Acids and Bases • Gilbert Lewis focused on the donation or acceptance of a pair of electrons during a reaction • Lewis Acid - electron pair acceptor • Lewis Base - electron pair donor • Most broadest of all 3 definitions; acids don’t even need hydrogen!

12. Neutralization

13. Acid-Base Reactions • Acid + Base = Water + Salt • Properties related to every day: • antacids depend on neutralization • farmers use it to control soil pH • formation of cave stalactites • human body kidney stones

14. Acid-Base Reactions • Neutralization Reaction - a reaction in which an acid and a base react in an aqueous solution to produce a salt and water: HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) H2SO4(aq) + 2KOH(aq) K2SO4(aq) + 2 H2O(l)

15. Steps - Neutralization reaction 1. A measured volume of acid of unknown concentration is added to a flask 2. Several drops of indicator added 3. A base of known concentration is slowly added, until the indicator changes color-measure the volume

16. Titration • Titration is the process of adding a known amount of solution of known concentration to determine the concentration of another solution • Remember? - a balanced equation is a mole ratio

17. Normality (N) • Useful to know the Molarity of acids and bases • Often more useful to know how many equivalents of acid or base a solution contains • Normality (N) of a solution is the concentration expressed as number of equivalents per Liter

18. Normality (N) • Normality (N) = equiv/L • equiv = Volume(L) x N; and also know: N=M x eq; M = N / eq • Diluting solutions of known Normality: N1 x V1 = N2 x V2 • N1 and V1 are initial solutions • N2 and V2 are final solutions