Neutralization reactions: Neutralization reactions involve acids and bases. There are several definitions of acids and bases. Acid: For the present, we can define an acid as a substance which, when added to water, yields one of more hydronium ions H3O+ – which is normally abbreviated by H+. (This is the Arrhenius definition of an acid). Example: HCl(aq) H+(aq) + Cl-(aq)

Base: (Arrhenius definition) A substance which, when added to water, yields one or more hydroxide ions.

Base: (Arrhenius definition) A substance which, when added to water, yields one or more hydroxide ions. Example: NaOH(aq) Na+(aq) + OH-(aq)

Acid-base neutralization reactions:

Acid-base neutralization reactions: Examples: HCl(aq) + NaOH(aq) NaCl(aq) + H2O H2SO4(aq) + 2 KOH(aq) K2SO4(aq) + 2 H2O

In verbal format, a neutralization reaction can be written as: acid + base salt + water Salt: A combination of a cation and an anion. Examples: NaCl, KBr, Li2SO4, NH4F.

Electron-transfer reactions (most frequently called redox reactions): These reactions involve an electron transfer process.

Electron-transfer reactions (most frequently called redox reactions): These reactions involve an electron transfer process. Example: 2 FeCl2(aq) + SnCl4(aq) 2 FeCl3(aq) + SnCl2(aq)

2 FeCl2(aq) + SnCl4(aq) 2 FeCl3(aq) + SnCl2(aq) can be stripped down to: 2 Fe2+ 2 Fe3+ + 2 e- (oxidation) and Sn4+ + 2 e- Sn2+ (reduction)

Reactions in solution

Reactions in solution Key terms Solution: A homogeneous (uniform) mixture of two or more substances.

Reactions in solution Key terms Solution: A homogeneous (uniform) mixture of two or more substances. Solvent: The medium into which the other substances are mixed or dissolved. It is the component of a solution usually present in the greater amount and in unchanged physical state. The most common solvent is water.

Solute: Any substance dissolved by the solvent.

Solute: Any substance dissolved by the solvent. Dilute solution: A solution in which the ratio of solute to solvent is small.

Solute: Any substance dissolved by the solvent. Dilute solution: A solution in which the ratio of solute to solvent is small. Concentrated solution: A solution in which the ratio of solute to solvent is large.

Solute: Any substance dissolved by the solvent. Dilute solution: A solution in which the ratio of solute to solvent is small. Concentrated solution: A solution in which the ratio of solute to solvent is large. Saturated solution: A solution in which no more solute will dissolve at a particular temperature.

Solute: Any substance dissolved by the solvent. Dilute solution: A solution in which the ratio of solute to solvent is small. Concentrated solution: A solution in which the ratio of solute to solvent is large. Saturated solution: A solution in which no more solute will dissolve at a particular temperature. Unsaturated solution: The ratio of solute to solvent is lower than that of a saturated solution. That is, more solute can be dissolved.

which the ratio of dissolved solute to solvent is Supersaturated solution: An unstable solution in which the ratio of dissolved solute to solvent is higher than that of a saturated solution.

which the ratio of dissolved solute to solvent is Supersaturated solution: An unstable solution in which the ratio of dissolved solute to solvent is higher than that of a saturated solution. Precipitation: The formation of a solid from solution.

which the ratio of dissolved solute to solvent is Supersaturated solution: An unstable solution in which the ratio of dissolved solute to solvent is higher than that of a saturated solution. Precipitation: The formation of a solid from solution. Precipitate: The solid formed in a solution.

which the ratio of dissolved solute to solvent is Supersaturated solution: An unstable solution in which the ratio of dissolved solute to solvent is higher than that of a saturated solution. Precipitation: The formation of a solid from solution. Precipitate: The solid formed in a solution. Solubility: The ratio of solute to solvent necessary to prepare a saturated solution at a given temperature.

Net Ionic Equations

Net Ionic Equations The principal idea is to strip a reaction in solution down to the essential chemistry taking place.

Net Ionic Equations The principal idea is to strip a reaction in solution down to the essential chemistry taking place. Example: What is the net ionic reaction for an acid-base reaction such as

Net Ionic Equations The principal idea is to strip a reaction in solution down to the essential chemistry taking place. Example: What is the net ionic reaction for an acid-base reaction such as NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) ?

There are several key questions to ask.

There are several key questions to ask. 1. Is the species a strong acid?

There are several key questions to ask. 1. Is the species a strong acid? 2. Is the species a strong base?

There are several key questions to ask. 1. Is the species a strong acid? 2. Is the species a strong base? 3. Is the species ionic or molecular?

There are several key questions to ask. 1. Is the species a strong acid? 2. Is the species a strong base? 3. Is the species ionic or molecular? 4. Is the species soluble in water?

There are several key questions to ask. 1. Is the species a strong acid? 2. Is the species a strong base? 3. Is the species ionic or molecular? 4. Is the species soluble in water? To answer these questions requires some factual information – i.e. a knowledge base.

Strong Acids Strong acid: A strong acid dissociates almost 100 % in water. E. g. in water HNO3(aq) H3O+(aq) + NO3-(aq) ess. 100%

Strong Acids The list of common strong acids is short. It is HCl HNO3 HClO3 HBr H2SO4 HClO4 HI Know this list. There are other more exotic strong acids, but these are not commonly encountered. Any acid not on this list can be regarded as weak.

Strong bases Strong base: A strong base dissociates almost 100 % in water. E. g. in water NaOH(aq) Na+(aq) + OH-(aq) ess. 100%

The list of common strong bases is short The list of common strong bases is short. It is LiOH NaOH KOH RbOH CsOH Ba(OH)2* * Solubility limited. Know this list. There are other more exotic strong bases, but these are not commonly encountered. Any base not on this list can be regarded as weak.

Ionic versus molecular

Ionic versus molecular

A. A typical metal combined with a typical nonmetal will yield an ionic compound.

A. A typical metal combined with a typical nonmetal will yield an ionic compound. B. A typical nonmetal combined with a typical nonmetal will yield a molecular compound.

A. A typical metal combined with a typical nonmetal will yield an ionic compound. B. A typical nonmetal combined with a typical nonmetal will yield a molecular compound. Lots of exceptions, particularly further down the periodic table.

Solubility issues

Now we are ready to address the original question!

Now we are ready to address the original question Now we are ready to address the original question! For the example, all 4 questions will come into play.

Now we are ready to address the original question Now we are ready to address the original question! For the example, all 4 questions will come into play. 1. Is the species a strong acid?

Now we are ready to address the original question Now we are ready to address the original question! For the example, all 4 questions will come into play. 1. Is the species a strong acid? 2. Is the species a strong base?

Now we are ready to address the original question Now we are ready to address the original question! For the example, all 4 questions will come into play. 1. Is the species a strong acid? 2. Is the species a strong base? 3. Is the species ionic or molecular?

Now we are ready to address the original question Now we are ready to address the original question! For the example, all 4 questions will come into play. 1. Is the species a strong acid? 2. Is the species a strong base? 3. Is the species ionic or molecular? 4. Is the species soluble in water?

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic. ionic. base NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic? ionic? base ? acid ? soluble?

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic. yes ionic NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic? yes ionic? no base ? yes acid ? yes soluble? yes

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic. yes ionic NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic? yes ionic? no base ? yes acid ? yes soluble? yes Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) Na+(aq) + Cl-(aq) + H2O(l)

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic. yes ionic NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic? yes ionic? no base ? yes acid ? yes soluble? yes Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) Na+(aq) + Cl-(aq) + H2O(l) Now cancel species that are common to both sides. Note – they must be exactly the same.

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic. yes ionic NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic? yes ionic? no base ? yes acid ? yes soluble? yes Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) Na+(aq) + Cl-(aq) + H2O(l) Now cancel species that are common to both sides. Note – they must be exactly the same. OH-(aq) + H+(aq) H2O(l)

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic. yes ionic NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l) strong strong ionic? yes ionic? no base ? yes acid ? yes soluble? yes Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) Na+(aq) + Cl-(aq) + H2O(l) Now cancel species that are common to both sides. Note – they must be exactly the same. OH-(aq) + H+(aq) H2O(l) This is the required net ionic equation for the reaction.

Example 2: Give the net ionic equation for the reaction: K2SO4(aq) + BaCl2(aq) 2 KCl + BaSO4 Note: The question does not tell you if KCl and BaSO4 are dissolved in solution.

For this example, only 2 questions will come into play (since we are not dealing with acids or bases in this example).

For this example, only 2 questions will come into play (since we are not dealing with acids or bases in this example). 3. Is the species ionic or molecular?

For this example, only 2 questions will come into play (since we are not dealing with acids or bases in this example). 3. Is the species ionic or molecular? 4. Is the species soluble in water?

K2SO4(aq) + BaCl2(aq) 2 KCl + BaSO4 ionic? ionic? ionic? ionic? soluble? soluble? soluble? soluble?

K2SO4(aq) + BaCl2(aq) 2 KCl + BaSO4 ionic. yes ionic. yes ionic K2SO4(aq) + BaCl2(aq) 2 KCl + BaSO4 ionic? yes ionic? yes ionic? yes ionic? yes soluble? yes soluble? yes soluble? yes soluble? no

K2SO4(aq) + BaCl2(aq) 2 KCl + BaSO4 ionic. yes ionic. yes ionic K2SO4(aq) + BaCl2(aq) 2 KCl + BaSO4 ionic? yes ionic? yes ionic? yes ionic? yes soluble? yes soluble? yes soluble? yes soluble? no Key comment: The subscript label “aq” tells you that the particular compound is soluble.