CH19 Bronsted-Lowry Definitions

Transcription

1 CH19 Bronsted-Lowry Definitions 1

2 BRONSTED-LOWRY DEFINITIONS [Acids] An acid is a substance that can donate H + ions HCl hydrochloric acid HNO 3 nitric acid HOAc acetic acid H hydronium ion NH + 4 ammonium ion H 2 S hydrogen sulfide HCO - 3 hydrogen carbonate H 2 O water More things are now considered acids 2

3 BRONSTED-LOWRY DEFINITIONS [Bases] A base is a substance that can accept H + ions NaOH sodium hydroxide Ca (OH) 2 calcium hydroxide NH 3 Ammonia CO 2-3 carbonate ion S 2- sulfide ion H 2 O water Not only substances that have OH - 3

4 BRONSTED-LOWRY DEFINITIONS [Hydronium Ion] H + + H 2 O H 3 O + hydronium ion H + proton; strongly attracted to H 2 O Simplicity H + 4

5 Bronsted Definitions ACIDS Donate [H + ] BASES Accept [H + ] Arrhenius Definitions ACIDS Produce [H + ] BASES Produce [OH - ] SALTS products of acid-base rxn 5

6 CH19 Conjugate Acid & Base Pairs 6

7 CONJUGATE ACID & BASE conjugate acid & conjugate base are used to emphasize the difference between acid & base (H + ) Def. conjugate: together Def. conjugate acid: a base gains H+ ion. Def. conjugate base: an acid donates H+ ion. Def. conjugate acid-base pair: a pair that differs by 1 H + A + B CB + CA acid base conjugate conjugate base acid 7

8 CONJUGATE ACID & BASE [EXAMPLES] NH 3(g) + H 2 O NH + 4 (aq) + OH - (aq) NH 3(g) + H 2 O NH + 4 (aq) +OH - (aq) NH + 4 (aq) + OH - NH (aq) 3(g) + H 2 O HCl (g) + H 2 O (l) H Cl (aq) - (aq) 8

9 CONJUGATE ACID & BASE So 1. an acid donates a proton and a base will accept it. 2. Anytime a proton is taken, it leaves a (-) behind 3. When one compound acts as an acid (donate H + ), another compound acts like a base (accept H + ) 4. H 2 O can function as a Bronsted Acid / Base. (amphoteric: substance functioning as both acids & bases). Monoprotic H Acid Diprotic 2H + Polyprotic 3H + or more 9

10 CONJUGATE ACID & BASE [EXAMPLES] H 2 CO 3 + OH - HCO H 2 O (Acid) (Base) (CB) (CA) HF + H 2 O F - + H 3 O + (Acid) (Base) (CB) (CA) H 2 SO 4 + H 2 O HSO H 3 O + HSO H 2 O SO H 3 O + 10

11 Warm up ACID + BASE SALT + H 2 O 1. H 2 SO 4 + NaOH + 2. H 3 PO 4 + Ca(OH)

12 Practice 3. Which substance (aqueous) conducts electricity: a. acid d. all of the above b. base e. none of the above c. salt f. only a & c 12

13 4. Name the following compounds: HOOCCOOH H 2 SO 4 K 2 S Cu 3 N 2 Practice 13

14 Practice 5. Which is a salt? a. HCl b. HNO3 c. KCl d. NaOH 14

15 Practice 6. A basic solution usually tastes: a. bitter b. salty c. sour d. sweet 7. Which is a property of an acid solution: a. feels soapy b. held together by ionic bonds c. tastes sour d. neutralizes buffer 15

16 Practice 8. Salt solutions: a. tastes bitter b. can conduct electricity c. have many hydrogen ions d. have many hydroxide ions 16

17 Practice 9. Which is a hydrogen-ion acceptor? a. CO b. HCl c. HClO2 d. NaOH 10. Cherries have a ph of about 4.0. They are a. Strong acids b. Strong bases c. Weak acids d. Weak bases ph Scale Strongly acidic neutral Strongly basic 17

18 Warm-up Fill in the missing information: 1.Arrhenius acids produce when dissolved in water. 2. Arrhenius bases produce when dissolved in water. 3. Brønsted-Lowry acid proton 4. Brønsted-Lowry base proton 18

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20 Practice Acids: a. donate hydrogen ions b. donate hydroxide ions c. accept anhydrous compounds d. accept inert compounds 20

21 Warm-up Write the formula for each compound: Barium Hydroxide Zinc Carbonate Iron( III) Iodide 21

22 ACID BASE Lemon juice, contains citric acid Vinegar contains ethanoic acid Acids usually have sour taste Many acids and bases are present in our everyday lives. Bases usually feel soapy and taste bitter 22

23 CH19 Self Ionization of Water 23

24 SELF-IONIZATION OF WATER H 2 O(l) + H 2 O(l) H 3 O + (aq) + OH - (aq) Hydronium Hydroxide K w = ion product constant K w = [H 3 O + ] [OH - ] or K w = [H + ] [OH - ] In pure 25 C, K w = 1.0 x [H + ] = [OH - ] = 1.0 x 10-7 M Based on [OH - ] & [H + ], solutions can be classified: 1. neutral [OH - ] = [H + ] = 1.0 x 10-7 M 2. acidic [H + ] > [OH - ] 3. basic [H + ] < [OH - ] 24

25 EXAMPLE 1 A solution has [H + ] = 1.0 X 10-2 M What will be the [OH - ] =? 25

26 EXAMPLE 2 A solution has [H + ] =0.0010M What is [OH - ] =? 26

27 PRACTICE Calculate [H + ] & [OH - ] for each of the following: a) 0.5 M HCl B) M Ba(OH) 2 C) 0.9M H 2 SO 4 27

28 PRACTICE Calculate [H + ] & [OH - ] for each of the following: a) 0.5 M HCl [H + ] = 0.5M [OH - ] = Kw / [H + ] = (1.0x10-14 ) / (0.5) = 2 x M B) M Ba(OH) 2 C) 0.9M H 2 SO 4 28

29 PRACTICE Calculate [H + ] & [OH - ] for each of the following: a) 0.5 M HCl [H + ] = 0.5M [OH - ] = Kw / [H + ] = (1.0x10-14 ) / (0.5) = 2 x M B) M Ba(OH) 2 [OH - ] = 0.020M x 2 = 0.040M [H + ] = Kw / [OH - ] = (1.0x10-14 ) / (0.040) = 2.5 x M C) 0.9M H 2 SO 4 29

30 PRACTICE Calculate [H + ] & [OH - ] for each of the following: a) 0.5 M HCl [H + ] = 0.5M [OH - ] = Kw / [H + ] = (1.0x10-14 ) / (0.5) = 2 x M B) M Ba(OH) 2 [OH - ] = 0.020M x 2 = 0.040M [H + ] = Kw / [OH - ] = (1.0x10-14 ) / (0.040) = 2.5 x M C) 0.9M H 2 SO 4 [H + ] = 0.9M x 2 = 1.8M [OH - ] = Kw / [H + ] = (1.0x10-14 ) / (1.8) = 5.6 x M 30

31 PRACTICE Calculate [H + ] & [OH - ] for each of the following: A) M Al (OH) 3 B) 0.90M H 3 PO 4 31

32 CH19 ph Scale 32

33 ph SCALE A more compact way to express [H + ] Soren Sorensen (Danish biochemist) ph= - log [H + ] poh= - log [OH - ] [H + ]= 10 -ph [OH - ]= 10 -poh Ex. Pure water: [H + ] = [OH - ] = 1.0 x 10-7 M Neutral ph=7.00 ph + poh =

34 ph SCALE 34

35 PRACTICE Calculate the ph, poh, [H + ] and [OH - ] for the following compounds: a M HCl b M NaOH c. ph = 2.96 d. ph =