reactions in aqueous solutions section 10.3. objectives describe aqueous solutions write complete...

Reactions in Aqueous Reactions in Aqueous SolutionsSolutions

Section 10.3

Objectives

Describe aqueous solutions Write complete ionic and net ionic

equations for chemical reactions in aqueous solutions

Predict whether reactions in aqueous solutions will produce a precipitate, water, or gas.

Key Terms

Solute Solvent Aqueous solution

Complete ionic equation Spectator ion Net ionic equation

Review of Solutions

Solvent- More plentiful substance in solution

Solute- The compound dissolved in the solvent

Aqueous solution- Solution in which the solvent is water

Aqueous Solutions Many possible solutes:

– Molecular compounds that exist as molecules

• Sucrose

• Ethanol– Molecular compounds that exist as ions

• HClHCl(g) H + (aq) = Cl- (aq)

Aqueous Solutions (cont)

– Ionic compounds that exist as ions

• NaOHNaOH(aq) Na + (aq) + OH- (aq)

Aqueous Solutions When two aqueous solutions containing ions

react it is always a double replacement reaction. The water does not react There are three possible products when aqueous

solutions react:– Precipitates– Water– Gases

Reactions that form Precipitates

Double-replacement reaction

2NaOH(aq) + CuCl2 (aq) 2NaCl (aq) + Cu(OH)2(s)

Ionic equations are used to show the details of reactions involving ions

Writing Ionic Equations You must show the reactants and the product as

ions A complete ionic equation shows all of the

particles in the solution as they realistically exist. A net ionic equation only shows particles that

participate in the reaction. To write a net ionic equation from a complete

ionic equation eliminate all spectators.

Complete Ionic Equations

AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)

What type of reaction is this? Ag+(aq) + NO3

-(aq) + Na+ (aq) + Cl-(aq) AgCl(s) + Na+ (aq) + NO3

-(aq)

Spectator Ions

Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) AgCl(s) + Na+(aq) + NO3-(aq)

Ions that are not directly involved in a reaction are called spectator ions– They appear on both sides of the arrow exactly

the same way

Net Ionic Equation

Eliminate spectators and rewrite the equation

Ag+(aq) + Cl-(aq) AgCl(s)

Ionic Equations

Make sure that the net charge is balanced. For example…

Pb(s) + 2Cl-(aq) PbCl2(s)

Reactions that Form Water

Double-replacement reactions Water molecules increase the number of

solvent particles No evidence of reaction is observable

(water is colorless and odorless)

HBr(aq) + NaOH(aq) H2O (l) + NaBr(aq)

Practice Write the complete ionic and net ionic

equations for the example:

HBr(aq) + NaOH(aq) H2O (l) + NaBr(aq)

Reactions that Form Gases

Double-replacement reactions Gas-producing Common gases:

– Carbon dioxide– Hydrogen cyanide– Hydrogen sulfide

Practice Write the complete and net ionic equations

for this gas-producing reaction:

2HI(aq) + Li2S(aq) H2S(g) + 2LiI(aq)

Homework

47-51 on page 299