IB Chemistry home > Syllabus 2016 > Energetics > Ionic compounds

Syllabus ref: 15.1

Ionic compounds are giant structures in which the simplest particles are ions. These ions are held together by strong electrostatic forces. The same laws of thermodynamics apply to ionic compounds as to covalent compounds. In this chapter we look at the application of the law of conservation of energy and Hess' law to ionic systems

Nature of science:

Making quantitative measurements with replicates to ensure reliability-energy cycles allow for the calculation of values that cannot be determined directly.


Essential idea: The concept of the energy change in a single step reaction being equivalent to the summation of smaller steps can be applied to changes involving ionic compounds

Representative equations (eg M+(g) M+(aq)) can be used for enthalpy/energy of hydration, ionization, atomization, electron affinity, lattice, covalent bond and solution.

Enthalpy of solution, hydration enthalpy and lattice enthalpy are related in an energy cycle.

Applications and skills

Construction of Born-Haber cycles for group 1 and 2 oxides and chlorides.

Construction of energy cycles from hydration, lattice and solution enthalpy. For example dissolution of solid NaOH or NH4Cl in water.

Calculation of enthalpy changes from Born-Haber or dissolution energy cycles.

Relate size and charge of ions to lattice and hydration enthalpies.

Perform lab experiments which could include single replacement reactions in aqueous solutions.

In Chapter 4.5