HL Energetics of Ionic Bond Formation 09/03/15

Energetics of Ionic Formation

What was covered:

The class started by handing in the previous homework (in this case, the 'Heat Death' poem).

The class then had a quick review on the HL information covered thus far in this chapter about 'Thermochemistry.' The review included a large packet covering thermochemistry and important definitions with their usage/purposes. 

Definitions:

• Atomisation - forming 1 mole of gaseous atoms
• Ionisation Energy - farming 1 mole of uni-positive ions in the gas phase
• Electron Affinity - forming 1 mole of uni-negative ions in the gas phase
• Lattice Energy - forming/ breaking 1 mole of ionic lattice from its constituent ions

Work in class:

In class the 'Born-Harper' cycle was covered step-by-step, on how to construct your own cycle.

A few examples were done in class, 2 with Mr. Carmichael and then some from the packet.

Example of 'Born-Harper Cycle':

To solve the lattice enthalpy, you would treat the cycle with Hess' law, saying enthalpy of formation is equal to the summation of all the other steps, for example:

Enthalpy of formation = (enthalpy of atomisation for Na)+(enthalpy of ionisation of Na)+(enthalpy of atomisation for Cl)+(enthalpy of electron affinity for Cl)+(lattice enthalpy)

-411=109+494+(242*.5)+(-364)+LE -> LE= -1580 kJ/mol

*It's important to note that the arrows pointing upwards will be positive values, and the arrows pointing downwards are of negative value (due to ex/endothermic reactions).

Homework:

The homework assigned for 11/03/15 was to complete the 2 last pages of questions 1-5.

Bibliography:

Born-Harper Cycle Diagram - "Further Enthalpy: Enthalpies, Born-Haber Cycle, Mean Bond Enthalpy." Further Enthalpy: Enthalpies, Born-Haber Cycle, Mean Bond Enthalpy. N.p., n.d. Web. 10 Mar. 2015.