Acids & Bases Unit 12

Intro to acids & bases Reflect: What does it mean to ‘ionize’ or ‘dissociate’?

Intro to Acids & Bases

Intro to Acids & Bases Do NOT react with metals

Intro to Acids & Bases acid base base acid base other (alcohol) base

pH Scale salt acid acid alcohol base acid acid & base base acid salt Reflect: Classify each of the following as an acid, base, salt, or alcohol. KCl HCl CH3COOH CH3OH NaOH H2SO4 H2O KOH LiBr HF salt acid acid alcohol base acid acid & base base acid salt

pH Scale pH Scale: Logarithmic scale that tells you the concentration of H+/H3O+ ions. Every time you move a unit of pH, the [H+] increased/decreases by a power of 10.

pH Scale

pH Scale & Indicators

pH Scale Indicators: They let you know if a chemical is an acid or a base by a color change. Methyl Orange: From 3.1-0 it will be red From 4.4-14 it will be yellow

pH Scale

pH Scale 4.4-8 Sample Problem 1: Which of the following substances would turn phenolphthalein pink? CH3OH HCl CH3COOH Ba(OH)2 Sample Problem 2: An unknown substance is found in a chemistry lab. It turns both methyl orange and thymol blue a yellow color. What pH range is possible for this substance? Alcohol Acid Acid 4.4-8

pH Scale & Indicators Sample Problem 3: Based on the results of testing colorless solutions with indicators, which solution is most acidic? A solution in which bromothymol blue is blue A solution in which bromcresol green in blue A solution in which phenolphthalein is pink A solution in which methyl orange is red

More pH scale & ionization of water

More ph scale & ionization of water

More pH scale & ionization of water The pH scale is logarithmic and therefore, moving 1 pH unit changes the concentration by 10x 100x pH=6 pH=6

Key Idea

pH Scale 12-base 6-acid 3-acid 13-base 8-base 10-base 2-acid 7-neutral

pH Scale

More pH scale & Ionization of water

More pH scale & ionization of water 12 6 3 13 8 10 2 7

Salts & Ionization of Water 9 Basic 13 Basic Buffer: A substance that resists a change in pH

Electrolytes

Electrolytes H+ Cl- H+ Cl- Cl- H+ H+ H+ H+ Cl- Cl- H+ Cl- H+ Strong Acid Weak Acid H+ Cl- H+ CH3COOH H+ Cl- Cl- H+ CH3COO- CH3COOH H+ H+ CH3COOH H+ Cl- Cl- H+ CH3COOH H+ Cl- H+ CH3COOH CH3COO- Strong acids completely ionize More ions = more electricity can be conducted. Weak acids only partially ionize Only a few ions = only some electricity can be conducted.

Electrolytes

HCl – stronger acid – more likely to dissociate – more ions Electrolytes Acid Salt Alcohol Base Acid Base Salt Alcohol HCl – stronger acid – more likely to dissociate – more ions

Titration Reflect: What does it mean to neutralize something? What is Molarity?

Titration

Titration Chemists perform acid/base neutralization reactions called Titrations. A Titration: Is an experiment that uses a buret to mix solutions together in very accurate amounts.   A way to find out the concentration (Molarity) of an acid or a base.

Titration 3. Uses a Standard Solution – an acid or base whose concentration is accurately known 4. Uses an End Point, signified by a color change in your indicator, as a way to tell you have created a neutral solution [acid ions] = [basic ions]

Titration If we want a neutral endpoint using Bromothymol Blue, we would want to titrate until we got a green color.

Titration: Reading a Buret

Titration The formula you should use when you see the words titration or neutralize is:

Titration

Titration

Titration

Titration MAVA = MBVB (0.100 M)(32 mL) = (0.35 M)VB VB = 9.14 mL (MA)(25 mL) = (0.40 M)(40 mL) MA = 0.64 M

MAVA = MBVB (0.100 M)(5.14 mL) = MB(10.61 mL) MB = 0.048 M Titration MAVA = MBVB (0.100 M)(5.14 mL) = MB(10.61 mL) MB = 0.048 M

[H2SO4] = 0.15 M MAVA = MBVB 2(0.15 M)(20 mL) = MB(50 mL) MB = 0.12 M Titration [H2SO4] = 0.15 M MAVA = MBVB 2(0.15 M)(20 mL) = MB(50 mL) MB = 0.12 M

MAVA = MBVB (0.2 M)(15.6 mL) = 2MB(4.0 mL) MB = 0.39 M Titration MAVA = MBVB (0.2 M)(15.6 mL) = 2MB(4.0 mL) MB = 0.39 M

Titration Problem 6: If 30.0 mL of carbonic acid is used to neutralize 1.5 M NH3, what volume of base will be neutralized by the acid, if the carbonic acid has a concentration of 1.0 M? MAVA = MBVB (2M)(30 mL) = (1.5M)(VB) VB = 40 M

Conjugate Acid-Base Pairs Reflect: What is the Arrhenius definition of: ACIDS BASES

Conjugate Acid-Base Pairs Arrhenius Acid/Base theory has some shortcomings: Limits acid/base reactions to aqueous solutions Does not explain why acids ionize Does not include bases without OH- ions (ex: NH3)

Conjugate Acid-Base Pairs Bronsted-Lowry (aka conjugate acid/base pairs): Bronsted- Lowry acids are proton (H+ ) donors Bronsted – Lowry bases are proton (H+ ) acceptors For example: H2CO3 + H2O  H3O+ + HCO3-

Conjugate Acid- Base Pairs Conjugate acid-base pairs : Are similar compounds that differ by the presence of one proton, or H+.

Conjugate Acid-Base Pairs Are similar compounds that differ by the presence of one proton (H+) Base Acid Conj. Acid Conj. Base Acid Base Conj. Base Conj. Acid

Conjugate Acid – Base Pairs Amphoteric: A substance that can act as either an acid or a base. (ex. H2O)

Conjugate Acid Base Pairs Practice Multiple Choice Ques. #1-12 2 1 4 3