Reactions in Aqueous Solutions: Metathesis Reactions and Net Ionic Equations Experiment 21 Page 227 Dr. Scott Buzby, Ph.D.
Objectives • To become familiar with writing equations for metathesis reactions • Understand the difference between molecular, ionic and net ionic equations • Determine the solubility of a salt by using solubility rules • Study the effect of temperature on solubilty
Definitions • Solubility • The property of a substance to dissolve in another substance to form a homogenous solution • Solute – The substance being dissolved • Solvent – The substance doing the dissolving • Aqueous solution – A solution where water is the solvent • Homogenous solution – A stable mixture that is uniform in composition where the solute will not settle out, no matter how long the solution sits, and it cannot be removed by physical means (ex. filtering) • Saturation • The point at which no more solute can dissolve in a solution and additional amounts of it will appear as a precipitate. • Precipitate • the formation of a solid in a solution • Electrolyte • any substance containing free ions that make the substance electrically conductive (ionic solution)
Metathesis Reaction • An aqueous chemical reaction in which the cations (+ Ions) and anions (- ions) appear to change partners • In order for a net change in the solution to occur (i.e. a reaction), ions must be removed from the solution by the formation of • a precipitate • a weak electrolyte or nonelectrolyte • a gas that escapes from solution
Metathesis Reaction Con’t. • Formation of a Precipitate • Formation of a Gas • Formation of a Weak Electrolyte
Ionic and Net Ionic Equations • Molecular Equation • Ionic Equation • Net Ionic Equation
Procedure • Part A: Metathesis Reactions • Mix the solutions in small test tubes and record your observations (precipitate, gas bubbles, heat, nothing) on the report sheet • Write out the three reactions according to your observations • Skip reactions 6 - 9 & 14 - 15
Procedure Con’t. • Part B: Solubility, Temperature and Crystallization • Prepare the solution as per instructions on Pg. 231 • Cool the solution to ~10°C by dipping beaker into ice water (DO NOT add ice to solution) and stirring carefully • Observe shape of crystals and filter COLD solution into an evaporating dish • Evaporate filtrate to half of its volume using a Bunsen burner and a ring stand (additional crystals should form) • Filter HOT solution into 100mL beaker and compare shape of crystals with first batch • Cool the filtrate to ~10°C with ice while stirring to obtain a third batch of crystals and compare shape with other two batches.
Homework – Due Next Week • Part A • Report Sheet – Pages 233 – 236 • Part B • Solubility Graph – Page 235 • Questions – Pages 235 – 236 • Questions • Page 236 • Pre-lab • Experiment #22 – Page 243