CHM 2045 Lecture Notes - Lecture 1: Lattice Energy, Exothermic Process, Sodium Chloride

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aquamarineshark960

18 Jan 2016

School

University of Florida

Department

Chemistry

Course

CHM 2045

Professor

John Mitchell

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There can be two definitions - one is the opposite of the other! Make sure you know which one is being used. The enthalpy change when one mole of an ionic lattice dissociates into isolated gaseous ions. Values: highly endothermic - there is a strong electrostatic attraction between, a lot of energy must be put in to overcome the attraction ions of opposite charge. The enthalpy change when one mole of an ionic crystal lattice is formed from its isolated gaseous ions. Values: highly exothermic - strong electrostatic attraction between ions of opposite charge, a lot of energy is released as the bond is formed, relative values are governed by the charge density of the ions. Q. j which substance in the the following pairs has the larger lattice enthalpy: nacl or kc, naf or nacl, mgcl2 or nacl, mgo or mgcl2. Oxides: thermal stability of group ii oxides decreases down the group.

Related Questions

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D. 1. Silver chloride is not soluble in water. What are the relative strengths of the intermolecular forces between Ag and Ciions and water molecules as compared to the intermolecular forces between water molecules and the forces that hold the silver chloride as a solid? a. The ionic attractions are stronger than the polar covalent bonds between the H' and O ions of the b. The ionic attractions are weaker than the intermolecular forces between the Ag' and Cr ions and water c. The ionic attractions are stronger than the intermolecular forces between the Ag' and Cr ions and water d. The ionic attractions are the same as the intermolecular forces between the Ag and CI ions and water water molecules. molecules. molecules molecules 2. The value of AHsotn for a water soluble compound is +34 kJ moÄ¾1. Which value for this compound would be numerically larger, its lattice energy or its hydration energy? Select the single best answer. step. b. The lattice energy, because it is the endothermic step c. The hydration energy, because it is the exothermic step. d. The lattice energy, because it is the exothermic step. 3, which of the following are reasons why the value of ì¨,on for a gas such as CO2, dissolving in water, is negative? a. When a gas dissolves in a liquid, there is no endothermic step as with the lattice energy of a solid. b. When a gas dissolves in a liquid, there is only an exothermic step as with the lattice energy of a solid. c. The only enthalpy change is the one associated with hydration, and this is always positive. d. The only enthalpy change is the one associated with hydration, and this is always negative. e. When a gas dissolves in a liquid the lattice energy is always higher than the hydration energy, making the net enthalpy always negative. 4. Why is ammonia so much more soluble in water than is nitrogen? a. The triple bond in nitrogen prevents it from dissolving in water. b. Nitrogen has only London forces, while both water and ammonia form hydrogen bonds. c. The molar mass of nitrogen is much larger than the molar mass of ammonia, which reduces its solubility. d. Diatomic molecules are never soluble in water s which agueous solution, if either, is likely to have the highÏr boiling point 50 m Nal or en-Na e au

The Born-Haber cycle is a series of steps that represent the formation of an ionic compound from a metal and a nonmetal. For example, the steps in a Born-Haber cycle for the formation of NaCl(s) consist of sublimation of the metal Na atom (ÎHsubl-Na) to form a gaseous Na atom, bond dissociation of the chlorine molecule (BECl2) to form a gaseous Cl atom, ionization energy of the sodium atom (IENa) to form a gaseous Na+ ion, electron affinity of the chlorine atom (EACl) to form a gaseous Cl- ion, and the lattice energy of NaCl (LENaCl) involving the coalescing of the gaseous Na+ and Cl- ions to form a solid NaCl formula unit.

With the above summary in mind, which particular steps of the Born-Haber cycle would be represented in the following reaction?

K(s) + Â½F2(g) â K(g) + F(g)

ÎHsubl-K and EAF

ÎHsubl-K, Â½BEF2, and EAF

ÎHsubl-K and Â½BEF2

IEK and Â½BEF2

CHM 2045 Lecture Notes - Lecture 1: Lattice Energy, Exothermic Process, Sodium Chloride

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