1. What are acids? Arrhenius acids produce H + ions in water. H 2 O HCl(g) H + (aq) + Cl - (aq) are electrolytes. have a sour taste. turn litmus red. neutralize bases. HCl Hydrochloric acid HNO 3 Nitric acid H 2 SO 4 Sulfuric acid 1

2. What are bases? Arrhenius bases produce OH − ions in water. taste bitter or chalky. are electrolytes. feel soapy and slippery. neutralize acids. NaOHsodium hydroxide KOHpotassium hydroxide 2

3. What are Brønsted-Lowry acids and bases? According to the Br Ø nsted-Lowry theory, acids donate a proton (H + ). bases accept a proton (H + ). In the reaction of ammonia and water, NH 3 base that accept H +. H 2 O acid that donates H +. 3

4. What is ionization of water! In water, H + is transferred from one H 2 O molecule to another. one water molecule acts as an acid, while another acts as a base. H 2 O + H 2 O H 3 O + + OH −........ :O: H + H:O: H:O:H + + :O:H −........ H H H water water hydronium hydroxide ion (+) ion (-) 4

5. However, pure water is neutral In pure water, the ionization of water molecules produces small, but equal quantities of H 3 O + and OH − ions. molar concentrations are indicated in brackets as [H 3 O + ] and [OH − ]. [H 3 O + ] = 1.0 x 10 − 7 M [OH − ] = 1.0 x 10 − 7 M Adding an acid to pure water increases the [H 3 O + ]. cause the [H 3 O + ] to exceed 1.0 x 10 -7 M. decreases the [OH − ]. 5 Adding a base to pure water increases the [OH − ]. causes the [OH − ] to exceed 1.0 x 10 − 7 M. decreases the [H 3 O + ].

6. Ion Product of Water, K w The ion product constant, K w, for water is the product of the concentrations of the hydronium and hydroxide ions. K w = [ H 3 O + ] [ OH − ] can be obtained from the concentrations in pure water. K w = [ H 3 O + ] [ OH − ] K w = [1.0 x 10 − 7 M] x [ 1.0 x 10 − 7 M] = 1.0 x 10 − 14 In neutral, acidic, or basic solutions, the K w is always 1.0 x 10 −14 6

7. Calculating [H 3 O + ] What is the [H 3 O + ] of a solution if [OH − ] is 5.0 x 10 -8 M? STEP 1: Write the K w for water. K w = [H 3 O + ][OH − ] = 1.0 x 10 −14 STEP 2: Rearrange the K w expression. [H 3 O + ] = 1.0 x 10 -14 [OH − ] STEP 3: Substitute [OH − ]. [H 3 O + ] = 1.0 x 10 -14 = 2.0 x 10 -7 M 5.0 x 10 - 8 7

8. An example! If lemon juice has [H 3 O + ] of 2 x 10 −3 M, what is the [OH − ] of the solution? K w = [H 3 O + ][OH − ] = 1.0 x 10 −14 [OH − ] = 1.0 x 10 -14 = 5 x 10 −12 M 2 x 10 - 3 8

9. pH Scale The pH of a solution indicate the acidity of a solution. values that usually range from 0 to 14. acidic when the values are less than 7. neutral with a pH of 7. basic when the values are greater than 7 determined using a) pH meter b) pH paper c) indicators that have specific colors at different pH values. 9

10. Calculating pH pH is the negative log of the hydronium ion concentration. pH = - log [H 3 O + ] Example: For a solution with [H 3 O + ] = 1 x 10 −4 pH =−log [1 x 10 −4 ] pH = - [-4.0] pH = 4.0 Note: The number of decimal places in the pH equals the significant figures in the coefficient of [H 3 O + ]. 4.0 1 SF in 1 x 10 -4 10

11. Calculating pH Find the pH of a solution with a [H 3 O + ] of 1.0 x 10 −3 : STEP 1 Enter [H 3 O + ] Enter 1 x 10 -3 by pressing 1 (EE) 3 The EE key gives an exponent of 10 and change sign (+/- key or – key) STEP 2 Press log key and change sign - log (1 x 10 −3 ) = -[-3] STEP 3 Adjust figures after decimal point to equal the significant figures in the coefficient. 3 3.00 Two significant figures in 1.0 x 10 −3 11

12. Neutralization Reactions In a neutralization reaction : an acid and a base produce a salt and water. an acid such as HCl reacts with a base such as NaOH. HCl + H 2 OH 3 O + + Cl − NaOHNa + + OH − the H 3 O + from the acid and the OH − from the base form water. H 3 O + + OH − 2 H 2 O HCl + NaOH NaCl + H 2 O acid base salt water 12

13. Balancing Neutralization Reactions Write the balanced equation for the neutralization of magnesium hydroxide and nitric acid. STEP 1 Write the acid and base. Mg(OH) 2 + HNO 3 STEP 2 Balance H + in acid with OH - in base. Mg(OH) 2 + 2HNO 3 STEP 3 Balance with H 2 O. Mg(OH) 2 + 2HNO 3 salt + 2H 2 O STEP 4 Write the salt from remaining ions. Mg(OH) 2 + 2HNO 3 Mg(NO 3 ) 2 + 2H 2 O 13

14. Buffers When an acid or base is added to water, pH changes drastically. to a buffer solution, pH is maintained; pH does not change. 14