ACIDS & BASES Important Aqueous Solutions

NC Essential Standards• 3.2.1 Classify substances using the hydronium and

hydroxide concentrations • Distinguish between acids and bases based on formula and

chemical properties• Differentiate between concentration (molarity) and strength (degree

of dissociation)• Use pH to identify acids and bases.• Interpret pH scale in terms of the exponential nature of pH values

in terms of concentrations.• Relate the color of indicator to pH using ranges provided in a table.• Compute pH, pOH, [H⁺] and [OH⁻]

• 3.2.2 Distinguish properties of acids and bases related to taste, touch, reaction with metals, electrical conductivity, and identification with indicators such as litmus paper and phenolphthalein.

Overview of Key Concepts • http://ed.ted.com/on/j4JlNr0Y#watch• Introduction 5 minutes

• Properties of acids and bases • http://

ed.ted.com/lessons/the-strengths-and-weaknesses-of-acids-and-bases-george-zaidan-and-charles-morton

Notes: Make 4 columns to easily jot down notes from the video• Acid properties Base properties Examples: Strong

Weak

Distinguish properties of acids and bases related to taste, touch, reaction with metals, electrical conductivity, and identification with indicators such as litmus paper and phenolphthalein.

Note: Think H+ ions when protons are used.

Review: Names and Formulas • Common acids that you must know• All are dissolved in water (aqueous solutions) • HCl• HBr• HF

• HNO₃• H₂SO₄• HC₂H₃O₂• H₂CO₃• H₃PO₄

Review: Names and Formulas• Common bases that you must know:

• NaOH• Mg(OH)₂

• NH₃

Acid & Base demonstrations • http://www.youtube.com/watch?v=ti_E2ZKZpC4

• Introduction - properties (5 minutes) • http://ed.ted.com/on/j4JlNr0Y

Arrenhius Definition of Acids and Bases

• Acids release H⁺ ion • Also known as hydronium ions (H₃O⁺)

• Bases release OH⁻¹ (hydroxide) ions

• Other definitions: • Bronsted Lowery • Lewis

pH scale

pH scale • pH values

• pH = - log [H⁺]

pH Scale

Strong Acids

Weak & Dilute Acids

Weak & Dilute Bases

StrongBases

Neutral⇓

Chemistry Reference TablesWhat do these formulas mean?

Ions in Solutions Neutral

[H⁺][OH⁻]

In water: [H⁺]= [ OH⁻] pH = 7 pOH = 7

pOH Scale

WeakBase

Weak & Dilute Bases

Weak & Dilute Acids

Strong Acids

Neutral⇓

pH + pOH = 14

Chemistry Reference Tables

Answers

Examples of Acids and Bases

pH Scale • http://www.johnkyrk.com/pH.html

pH indicators • What is the approximate pH of the solution tested in

the picture? Is the solution an acid or a base? Is it strong or weak?

pH Indicators • Litmus Paper • Phenolphthalein

Blue - indicates baseRed - indicates acid

Litmus (pH indicator)

below pH 4.5

above pH 8.3

4.5 ↔ 8.3

pH below 8

pH 8 - 12 pH above 12

Colorless Fuchsia Colorless

pH Indicators - different indicators for different purposesScientist choose indicators based on the solution and process to be monitored.

Bromothymol BlueAcid = yellowNeutral = greenBase = blue

pH range Description Colour<3 Strong acid Red

3-6 Acid Orange/Yellow

7 Neutral Green

8-11 Alkali Blue

> 11 Strong alkali Violet/Purple

Universal Indicator

Strength of Acids and Bases • http://

ed.ted.com/lessons/the-strengths-and-weaknesses-of-acids-and-bases-george-zaidan-and-charles-morton

• 4 minutes

• Write notes:

Concentration⇎ Strength • Concentrated or dilute - Molarity

• 6M vs. 0.6 M

Strength or weak = degree to which acids or bases separate into ions

Strength vs. Concentration • Strength in acids

• Based on degree H⁺ ions separate from the anion

• Proportion of acid molecules in which H⁺ separate compared to how many acid molecules do not separate

• Strong acids = most H⁺ separate • Examples: HCl, HNO₃ and H₂SO₄

• Weak acids = only some H⁺ separate • Examples: HF, HC₂H₃O₂

• Strength of Bases • Strong = most OH⁻ separate from the metal

Reacting acids and bases• HCl (aq) + Na(OH) (aq) → HOH + NaCl

• Write the word formula• Identify the type of chemical reaction

• What is happening with the reactants and products?

• Ionic equation: • Solubility rules:

Neutralization reactions• Special double replacement reaction• Always:• Reactants: Acid + Base (any order) • Products: Salt (ionic compound) + Water

• Practice: •

• sulfuric acid and calcium hydroxide

Neutralization reactions• Acid + Base → Salt + Water • sulfuric acid and calcium hydroxide

• potassium hydroxide and nitric acid

• carbonic acid and magnesium hydroxide

• hydrobromic acid and lithium hydroxide

Salts formed in the previous problems

sulfuric acid and calcium hydroxidesalt name: calcium sulfate salt formula: CaSO4

potassium hydroxide and nitric acid salt name: potassium nitrate salt formula: KNO3

carbonic acid and magnesium hydroxidesalt name: magnesium carbonate salt formula: MgCO3

hydrobromic acid and lithium hydroxidesalt name: lithium bromide salt formula: LiBr