REACTIONS IN AQUEOUS SOLUTIONS: METATHESIS REACTIONS AND NET IONIC EQUATIONSExperiment 21Page 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

BXAYBYAX

METATHESIS REACTION CON’T.

Formation of a Precipitate

Formation of a Gas

Formation of a Weak Electrolyte

)()(3)(3)( saqaqaq AgClNaNOAgNONaCl

)(2)()(2)( 22 gaqaqaq SHNaClSNaHCl

)(2)()()( laqaqaq OHNaClNaOHHCl

IONIC AND NET IONIC EQUATIONS

Molecular Equation

Ionic Equation

Net Ionic Equation

)()(3)(3)( saqaqaq AgClNaNOAgNONaCl

)()(3)()(3)()()( saqaqaqaqaqaq AgClNONaNOAgClNa

)(sAgClClAg

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