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Exam_II_Review_Guide - Exam II and 15 Has not been check by...

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Exam II: Chapters 10, 14, and 15 – Has not been check by Sweeder KEY ||||| = useful equations ||||| = definitions ||||| = key ideas Chapter 10: Bonding and Molecular Structure: Orbital Hybridization and Molecular Orbital s Molecular Orbital Theory MO theory assumes that pure s and p atomic orbitals of the atoms in the molecule combine to produce orbitals that are delocalized over several atoms or even an entire molecule. Those orbitals are called molecular orbitals 1 st principle of molecular orbital theory: the total number of molecular orbitals is always equal to the total number of atomic orbitals contributed by the atoms that have combined 2 nd principle of molecular orbital theory: the bonding molecular orbital is lower in energy than the parent orbitals, and the antibonding orbital is higher in energy 3 rd principle of molecular orbital theory: electrons of the molecule are assigned to orbitals of successively higher energy Bond order = ½ (number of e - s in bonding MOs –number of e - s in antibonding MOs) 4 th principle of MO theory: atomic orbitals combine to form molecular orbitals most effectively when the atomic orbitals are of similar energy Chapter 14: Solutions and Their Behavior Molality of solute (m) = amount of solute (moles) / mass of solvent (kg) Mole fraction: the amount of that component divided by the total amount of all of the components in the mixture Mole fraction of A (X A ) = n A / (n A + n B + n C + …) The sum of the mole fractions of the components in the solutions equals 1.000. This holds true for the solute and solvent in all solutions Weight percent: mass of one component divided by the total mass of the mixture, multiplied by 100% Weight % of A = [mass of A / (mass of A + mass of B + mass of C + …)] × 100% If you know the weight percent of a solute, you can determine its mole fraction of molality Parts per million (ppm) is often used to express concentration. It refers to relative amounts by mass Units of ppm and mg/L are approximately equal 1.0 ppm = 1.0 g of a substance in a sample with ba total mass of 1.0 million g. Liquids Dissolving in Liquids If 2 liquids mix to an appreciable extent to form a solution, they are said to be miscible Immiscible liquids do not mix to form a solution; they exist in contact with each other as separate layers
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“like dissolves like” o 2 or more nonpolar liquids or 2 ore more polar liquids are both usually miscible o Basis of “like dissolves like” With H 2 O and C 2 H 5 OH, the major force between molecules is hydrogen bonding in the –OH groups.
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