Chapter 3 Notecards

  1. Acid Strength
    the strength of an acid is related to its acidity constant, Ka or its pKa. The larger the value of its Ka or the smaller the value of its pKa, the stronger the acid.
  2. Acidity Constant (Ka)
    an equilibrium constant related to the strength of an acid
  3. Base Strength
    this is inversely related to the strength of its conjugate acid; the weaker the conjugate acid, the stronger this is. In other words, if the conjugate acid has a large pKa, the base will be strong.
  4. Bronsted-Lowry Acid
    a substance that can donate or lose a proton
  5. Bronsted-Lowry Acid-Base Theory
    an acid is a substance that can donate or lose a proton; a base is a substance that can accept or remove a proton. The conjugate acid of the base is the molecule or ion that forms when a base accepts a proton. The conjugate base of an acid is a molecule or ion that forms when and acid loses its proton.
  6. Bronsted-Lowry Base
    a substance that can accept or remove a proton
  7. Carbanion
    a chemical species in which a carbon atom bears a formal negative charge
  8. Carbocation
    a chemical species in which a trivalent carbon atom bears a formal positive charge
  9. Conjugate Acid
    the molecule or ion that forms when a base accepts a proton
  10. Conjugate Base
    the molecule or ion that forms when an acid loses its proton
  11. Curved Arrows
    these show the direction of electron flow in a reaction mechanism. They point from the source of an electron pair to the atom receiving the pair. Double-barbed types are used to indicate the movement of a pair of electrons; single-barbed types are used to indicate the movement of a single electron. These are never used to show the movement of atoms.
  12. Delocalization Effect
    the dispersal of electrons, or of electrical charge. It’s effect on a charge always stabilizes a system
  13. Electrophiles
    a Lewis acid, an electron-pair acceptor, an electron-seeking reagent.
  14. Endothermic Reactions
    a reaction that absorbs heat
  15. Energy
    the capacity to do work
  16. Enthalpy Change (∆H)
    also called the heat of reaction. Used to measure the change in heat after system and its standard state has undergone a transformation to another system, also in its standard state for a reaction, this is a measure of the difference in the total bond energy of the reactants and products. It is one way of expressing the change in potential energy of molecules as they undergo reaction. This is related to the free-energy change, and to the entropy change, through the expression:∆H = ∆G + T∆S
  17. Entropy Change (∆S)
    this is the change in order between two systems in their standard states. This has to do with changes in the relative order of a system. The more random a system is, the greater bases. When a system becomes more disorderly, this is positive.
  18. Equilibrium Constant (Keq)
    a constant that expresses the position of an equilibrium. This is calculated by multiplying the molar concentrations of the products together and then dividing this number by the number obtained by multiplying together the molar concentrations of the reactants.
  19. Exothermic Reactions
    a reaction that involves heat. For these reactions, ∆H is negative.
  20. Free-Energy Change (∆G)
    this is one way to measure the change in energy between two systems in their standard states. A negative value for a reaction means that the formation of products is favored when the reaction reaches equilibrium.
  21. Heterolysis
    the cleavage of a covalent bond so that one fragment departs with both of the electrons of the covalent bond that joined them. This effect on a bond normally produces positive and negative ions.
  22. Intermediates
    the transient species that exists between reactants and products in a state corresponding to a local energy minimum on a potential energy diagram
  23. Ionic Reaction
    a reaction involving ions as reactants, intermediates, or products. These occur through the heterolysis of covalent bonds.
  24. Kinetic Energy
    energy that results from the motion of an object. KE = ˝mv2 where m is the mass of the object and v is its velocity.
  25. Leveling Effect of the Solvent
    an effect that restricts the use of certain solvents with strong acids and bases. In principle, no acid stronger than the conjugate acid of a particular solvents can exist to an appreciable extent in that solvents, and no base stronger than the conjugate base of the solvent can exist to an appreciable extent in that solvent
  26. Lewis Acid-Base Theory
    an acid is an electron pair acceptor, and the base is an electron pair donor.
  27. Nucleophile
    a Lewis base, an electron pair donor that seeks a positive center in a molecule.
  28. Oxonium Ion
    a chemical species with an oxygen atom that bears a formal positive charge.
  29. pKa
    the negative logarithm of the acidity constant, Ka. pKa = -log Ka.
  30. Potential Energy
    stored energy; it exists one attractive or repulsive forces exist between objects.
  31. Protic Solvent
    a solvents whose molecules have a hydrogen atom attached to a strongly electronegative element such as oxygen or nitrogen. Molecules of this can therefore form hydrogen bonds to unshared electron pairs of oxygen or nitrogen atoms of solute molecules are ions, thereby stabilizing them.
  32. Reaction Mechanism
    a step-by-step description of the events that are postulated to take place at the molecular level as reactants are converted to products. Each individual step will include a description of all intermediates and transition states. Each step proposed for reaction must be consistent with all experimental data obtained for the reaction.
  33. Resonance
    an effect by which a substituent exerts either an electron-releasing or electron-withdrawing effects through the π system of the molecule
  34. Resonance Structures
    Lewis structures that differ from one another only in the position of their electrons. A single example of these will not adequately represent a molecule the molecule is better represented as a hybrid of all of the examples
  35. Spectator Ions
    ions that play no part in the acid-base reaction
  36. Substituent Effect
    an effect on the rates of reaction, or on the equilibrium constant, caused by the replacement of a hydrogen atom by another atom or group. This includes the effects caused by the size of the atom or group, called steric effects, and those effects caused by the ability of the group to release withdrawing electrons, called electronic effects. Electronic effects are further classified as being inductive effects for resonance effects.
  37. Substitution Reaction
    a reaction in which one group replaces another in a molecule
Card Set
Chapter 3 Notecards
Chapter 3 Acids and Bases