Chemistry 2

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• Publisher: QuickStudy Reference Guides
• Year: 2018
• Print ISBN: 9781423233046
• eBook ISBN: 9781423237501
• Topic: Biological Sciences
• Subtopic: Teaching Science & Technology
• Index: Biological Sciences

Answers at your fingertips to the essentials of a subject that is challenging at best and that many students struggle with. The 6 page laminated guide focuses on physical chemistry with the details and structure of the subject organized and designed to be a key to the answers that are further supported by your texts and lectures. Use as a review before testing, or as a memory companion that keeps your mind focused on the whole course daily, weekly, or as needed before exams. Suggested uses:
o Students – especially relevant for those majoring in engineering, science, or a health care related field
o Quick Reference – instead of digging into the textbook to find a core answer you need while studying, use the guide to reinforce quickly and repeatedly
o Memory – refreshing your memory repeatedly is a foundation of studying, have the core answers handy so you can focus on understanding the concepts
o Test Prep – no student should be cramming, but if you are, there is no better tool for that final review

Acids & Bases

Arrhenius Definition

• Acids produce H+ ions in aqueous solutions
  HCl (aq) → H⁺ (aq) + Cl^- (aq)
  • H⁺ ions react with water to form H₃O⁺ (hydronium) ions
• Bases produce OH^- ions in aqueous solutions
  NaOH (aq) → Na⁺ (aq) + OH^- (aq)
• Acids and bases form water and neutralize each other
  H⁺ (aq) + OH^- (aq) → H₂O (l)

Bronsted-Lowry Definition

• Acids are proton (H⁺) donors
  HCl (aq) + H₂O (l) → H₃O⁺ (aq) + Cl^- (aq)
  • HCl is an acid because it donated a H⁺ to H₂O
• Bases are proton (H⁺) acceptors
  NH₃ (aq) + H₂O (l) → NH₄⁺ (aq) + OH^- (aq)
  • NH₃ is a base because it accepted the H⁺ from H₂O
• Conjugate acid-base pairs: Transfer of a proton
  H₂SO₄ (aq) + H₂O (l) → HSO₄^- (aq) + H₃O⁺ (aq)

Lewis Definition

• Transfer of electron pairs
  • Acids are electron pair acceptors
  • Bases are electron pair donors
• A substance doesn’t need to contain hydrogen to be an acid

• BF₃ has an empty orbital and can accept an electron pair from NH₃
• The product of a Lewis acid-base reaction is called an adduct
• The Lewis definition creates a new class of acids
• Lewis acids have empty orbitals
• Molecules with incomplete octets act as Lewis acids
• Molecules with complete octets act as Lewis acids and may rearrange electrons
• Some cations act as Lewis acids and have empty octets

Acid & Base Strengths

• Strong acids completely ionize in a solution HCl (aq) + H₂O (l) → H₃O⁺ (aq) + Cl^- (aq)
  • A 1.0 M HCl solution has [H₃O⁺] of 1.0 M
• Weak acids partially ionize in a solution HF (aq) + H₂O (l) ↔ H₃O⁺ (aq) + F^- (aq)
  • A 1.0 M solution HF has [H₃O+] less than 1.0 M
• General formula:
  HA (aq) + H₂O (l) ↔ H₃O⁺ (aq) + A^- (aq)
  HA (aq) ↔ H⁺ (aq) + A^- (aq)
• Autoionization: Water acts as an acid and a base
  H₂O (l) ↔ H⁺ (aq) + OH^- (aq)
  K_w = [H₃O⁺][OH^-] = [H⁺][OH^-] = 1.0×10^-14
• Neutral solution:
  [H₃O⁺] = [OH^-] = 1.0×10^-7 M at 25°C
• Acidic solution: [H₃O⁺] > [OH^-]
• Basic solution: [H₃O⁺] < [OH^-]

Scales

• pH: Measure of the acidity of a solution
  pH = -log [H₃O⁺]
  • pH > 7: Basic solution
  • pH < 7: Acidic solution
  • pH = 7: Neutral solution
• pOH: Uses [OH^-]
  pOH = -log [OH^-]
  • pOH < 7: Basic solution
  • pOH > 7: Acidic solution
  • pOH = 7: Neutral solution
• pH + pOH = 14.00 at 25°C
• pK_a = -log K_a
• Small K_a: Strong acid
• The relative strength of weak acids is determined by the acid ionization constant

K_a =

[H3O^+][A^−]

[HA]

• ICE charts: Compare initial concentrations, changes, and concentrations at equilibrium
  HA (aq) + H₂O (l) ↔ H₃O⁺ (aq) + A^- (aq), where: [HA] is 0.10 M
  • The initial [H₃O⁺] is roughly 0.00—a small amount from the autoionization of water

K_a =

[H3O^+][A^−]

[HA]

= K_a =

x^2

0.10 − x

, where:

• • • x is the amount of HA ionized
    • x is usually very small and can be ignored in most circumstances
    • If x isn’t very small, use the quadratic equation to solve

	[HA]	[H3O^+]	[A^-]
Initial	0.10	~0.00	0.00
Change	-x	+x	+x
Equilibrium	0.10 − x	x	x

• Percent ionization: Weak acids; percent of the initial acid that ionizes
  • Percent ionization =

    (Concentration of ionized acid)

    (Initial concentration of acid)

    × 100%
• Strong bases completely dissociate
  • NaOH (aq) → Na⁺ (aq) + OH^- (aq)
  • Most strong bases are in group 1A or 2A of the periodic table
• Weak bases don’t completely dissociate
  NH₃ (aq) + H₂O (l) ↔ NH₄⁺ (aq) + OH^- (aq)
• Base ionization constant: Kb
• Generic formula:
  B (aq) + H₂O (l) ↔ BH⁺ (aq) + OH^- (aq)
  K_b =

  [BH^+][OH^-]

  [B]

  K_a× K_b = K_w = 1.0 × 0^-14 at 25°C
  pK_a + pK_b = 14
• Salt: Result of the neutralization of an acid and base; ionic compound
  • Has both a cation and an anion
  • Can form acids, bases, or neutral solutions in water
    • When the cation and anion are both neutral, it forms a pH neutral solution in water
    • When the cation is neutral and the anions are a conjugate base of weak acid, it forms a basic soluti...

Table of contents

• Intermolecular Forces
• Changes in Matter
• Solutions
• Chemical Kinetics
• Acids & Bases
• Thermodynamics
• Electrochemistry
• Radioactivity