Acids & Bases
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Transcript of Acids & Bases
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ACIDS & BASES Important Aqueous Solutions
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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.
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Overview of Key Concepts • http://ed.ted.com/on/j4JlNr0Y#watch• Introduction 5 minutes
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• 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.
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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
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Review: Names and Formulas• Common bases that you must know:
• NaOH• Mg(OH)₂
• NH₃
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Acid & Base demonstrations • http://www.youtube.com/watch?v=ti_E2ZKZpC4
• Introduction - properties (5 minutes) • http://ed.ted.com/on/j4JlNr0Y
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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
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pH scale
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pH scale • pH values
• pH = - log [H⁺]
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pH Scale
Strong Acids
Weak & Dilute Acids
Weak & Dilute Bases
StrongBases
Neutral⇓
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Chemistry Reference TablesWhat do these formulas mean?
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Ions in Solutions Neutral
[H⁺][OH⁻]
In water: [H⁺]= [ OH⁻] pH = 7 pOH = 7
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pOH Scale
WeakBase
Weak & Dilute Bases
Weak & Dilute Acids
Strong Acids
Neutral⇓
pH + pOH = 14
Chemistry Reference Tables
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Answers
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Examples of Acids and Bases
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pH Scale • http://www.johnkyrk.com/pH.html
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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?
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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
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pH Indicators - different indicators for different purposesScientist choose indicators based on the solution and process to be monitored.
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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
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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:
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Concentration⇎ Strength • Concentrated or dilute - Molarity
• 6M vs. 0.6 M
Strength or weak = degree to which acids or bases separate into ions
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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
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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:
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Neutralization reactions• Special double replacement reaction• Always:• Reactants: Acid + Base (any order) • Products: Salt (ionic compound) + Water
• Practice: •
• sulfuric acid and calcium hydroxide
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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
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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