Net Ionic Equations

Keq and Different Reactions

Chem 12

​Syllabus dot points

• ​5.3 e

• explore the use of Keq for different types of chemical reactions, including but not limited to: – dissociation of ionic solutions – dissociation of acids and bases

​What we will be covering...

• ​what is solubility equilibria

• ​dissociation of acids and bases

• ​practice questions

​Solubility Equilibria

• ​a state of dynamic equilibrium that exists when a solid species dissociates into an ionic solution of that species

• dissociation = where a species splits into a smaller molecule (usually an ion)

• ​have to determine net ionic equations (Year 11)

  • ​then 'convert' to an equilibrium equation, where the solid is on the reactant side

​K_sp

• ​the equilibrium expression for dissolved ionic solid solutions is called the solubility product

• ​don't include the solids as part of a heterogenous system

• ​value wise --> the smaller the Ksp for a precipitate, the less solubility it has

• ​only used when the system is at equilibrium, if it isn't, we are just measuring Q, or the ionic product

​Dissociation of acids and bases

• ​go into more detail in Module 6

• ​strong and weak

  • ​strong = complete ionisation in water

  • ​weak = partial ionisation in water

​Dissociation of acids: Ka

• When a weak acid only partially dissociates in water you get an equilibrium system, with: the acid, hydrogen ions, and the anion of the acid

• The larger the Ka - the larger the degree of dissociation

​Dissociation of bases: Kb

• Same as for acids. Weak bases produce an equilibrium system where the base, hydroxide ions, and the cation of the base is present

​Next up:

Solution equilibria