What do you do when you find a dead chemist?

You BARIUM!

Journal Entry #2 What went well on the test? What did you struggle with? What will you change to prepare for the next test? Solve: How many moles are present in a solution of NH 3 with a concentration of 0.5 mol/L and 2.0 L of volume?

Precipitation Reactions Ionic compounds – Made of a metal (cation) ex. Na + Al 3+ – Made of a non-metal (anion) ex. F - S 2- – Examples: NaCl MgF 2 (remember the criss-cross rule) When placed in water, they dissolve or the ions break apart and become surrounded by a polar liquid NaCl(s)  Na + (aq) + Cl - (aq)

Opposite of dissolving in precipitation! Double displacement reactions in which two aqueous solutions are mixed and a precipitate forms NaCl (aq) + AgNO 3(aq)  Precipitation Reactions

Molecular Equations Pb(NO 3 ) 2(aq) + KI (aq)  Show intact, undissolved reactants and products How do we predict which product will be the precipitate?

Solubility Charts Find the substance’s negative ion (anion) Use the table to match with the substance’s positive ion (cation) Your results will be: – Soluble (no precipitate) – Slightly soluble or insoluble (precipitate)

Lead (II) nitrate/potassium iodide Pb(NO3) 2 – Cation  Pb 2+ – Anion  NO 3 - KI – Cation  K + – Anion  I - PbI 2 Insoluble & therefore won’t break apart KNO 3 Cation  K + Anion  NO 3 -

Pb 2+ (aq) + 2NO 3 - (aq) + 2K + (aq) + 2I - (aq)  PbI 2(s) + 2K + (aq) + 2NO 3 - (aq) NOW, cancel all spectator ions (any doubles) on either side of  Net ionic equation: Pb 2+ (aq) + 2I - (aq)  PbI 2(s) Ionic Equation

Example: Write a net ionic equation for the reaction between barium chloride and sodium sulfate