A saturated solution of Cd(OH)2 is shown in the middle beaker. If hydrochloric acid solution is added, the solubility of
Cd(OH)2 will increase, causing additional solid to dissolve. Which of the two choices, Beaker A or Beaker B, accurately represents the solution after equilibrium is reestablished? (The water molecules and Cl- ions are omitted for clarity.) [Sections]
Chapter 7—Sections 7.1-7.3 Section 7.1 v The VSPER Model • VSPER model: The electron pairs in a valance shell of the atom repel each other. Since they repel each other, they will also transform into different shapes from doing so. • Electron domain (pair): a lone pair or a bond of electrons (double or single dot on lewis structure). • There are a variety of shapes the molecules can take on. - 2 bonds: linear - 3 bonds: trigonal planar - 4 bonds: tetrahedral or trigonal bipyramidal - 5 bonds: octahedral v Electron Domain Geometry and Molecular Geometry • Electron domain geometry: the way the electron domains are arranged around the central atom. • Bond angle: the angle between 2 adjacent bonds. • Equatorial bond: the bonds that are arranged in a trigonal plane. • Axial bond: two bonds which are formed by an axis that is perpendicular to the trigonal plane. v Deviation from Ideal Bond Angles • Lone pairs take up a lot more space than bonding pairs. • Lone pairs on central atoms are attracted to the nucleus of the atom only. • The bonding pairs on central atoms are attracted by the nuclei of the bonding atoms (both of them). • Multiple bonds repel more strongly that single bonds due to them being more electron dense. Section 7.2 • Molecular geometry helps us understand the physical and chemical behaviors of a substance. Sec tion 7.3 • Intermolecular forces: the attractive forces between molecules that surround each other. • Van der waals forces: the attractive forces in a pure substance that act between atoms or molecules. These include hydrogen bonding, dispersion forces, and dipole-dipole interactions. v Dipole-Dipole Interactions • Dipole-dipole interactions: attractive forces that act between polar molecules. Chapter 7—Sections 7.1-7.3 • The attractive force between polar molecules is coulombic, so the magnitude of the dipole is what determines the magnitude of the attractive forces. v Hydrogen Bonding • Hydrogen bonding: a special kind of dipole-dipole interaction. - Occurs only in molecules in which the hydrogen is bonded to a small and very electronegative atom. v Ion-Dipole Interaction • Ion-diploe interactions: attractions between positive ions, negative ions, and polar molecules. These are coulombic interactions. • The magnitude of an ion-dipole interaction is dependent on the ion size and dipole moment, and the polar molecule size. - Since they are smaller, cations have a stronger interaction with dipoles than anions do.