Chemical Reactions Chapter 4. The Periodic Table Review –Arrangement is based on increasing . –Groups or columns Elements within a group have

Chemical Reactions

Chapter 4

The Periodic Table

• Review– Arrangement is based on increasing ____ ____.– Groups or columns

• Elements within a group have similar ____ and _____ properties.

• Alkali metals (Group __), alkaline earth metals (Group __), halogens (Group __), and noble gases (Group ___).

– s, p, d, and f blocks

Properties of Metals, Nonmetals and Metalloids


• The stair sep line separates the metals from the nonmetals– Metals are to the left of this line

• ~80% of the elements are metals

– Nonmetals are to the right of this line– Metalloids are on the line (in green)

• Metalloids or semimetals exhibit properties intermediate between metals and metalloids.

– For semiconductors such as silicon, the conductance increases with temperature

Typical properties exhibited by metals and nonmetals are given in Tables 4-3 and 4-4.


• Metallic character increases from top to bottom and decreases from left to right.

• Nonmetallic character decreases from top to bottom and increases from left to right.– Best nonmetals are far to the right

PeriodicChart

MoreMetallic

Less Metallic

Aqueous Solutions

• An aqueous solution exists when a solute is dissolved in _____.– Formula is followed by (__)

• An electrolyte is a substance whose aqueous solution _____ ______ due to the movement of ions or charged particles.– An electrolyte produces ____ when dissolved

in water. For example, NaCl dissolved in water to produce Na+ and Cl- ions.

Aqueous Solutions

• The more ions produced by the substance, the stronger the electrolyte– Strong electrolyte – substances that conduct

electricity well in dilute aqueous solutions– Weak electrolyte – substances that conduct

electricity poorly in dilute aqueous solution– Nonelectrolyte – substances that do not conduct

electricity in aqueous solutionsDEMO: NaCl, acetic acid, and sugar water

Generation of Ions in Solution

• Ions are generally produced from a substance in water by either dissociation or ionization.– Dissociation – an _____ compound separates

into ions in solution• NaCl(s)

– Ionization – a ______ compound separates or reacts with water to form ions in solution

• HNO3(aq) + H2O(l) H3O+(aq) + NO3-(aq)

Generation of Ions in Solution

• Strong electrolytes. These are soluble in water.– Strong acids– Strong bases– Most soluble salts

• Weak electrolytes. – Weak acids– Weak bases

Acids and Bases• An acid is a substance that____ a proton.

– In aqueous solution, this proton combines with water to form H3O+. All acids are ________ substances.

– Strong acids• Ionize almost completely to form ions in dilute aqueous

solutions.– Original acid molecules largely do not exist in solution.– Ionization is near 100%

• A list of strong acids is given in Table 4-5 (know these).

Acids and Bases• Representing reactions between strong acids and water.

• The double arrow indicates that the reaction proceeds in both directions. The reaction is ______. In reactions with double arrows, the limiting reactant is not all used up.– The longer arrow pointing to the right indicates the the reaction

is product-favored.– Ionization is near ________, only a _____ amount of limiting

reactant remains.– All strong acids react similarly in water. They are product-

favored.

HClO3(aq) + H2O(l) H3O+(aq) + ClO3

-(aq)HClO3(aq) + H2O(l) H3O+(aq) + ClO3

-(aq)

Acids and Bases

• Weak acids ionize only _____ in dilute aqueous solutions.– Ionization is generally less than 5%.– A list of common weak acids is in Table 4.6.

– The reaction is also reversible, but the longer arrow points to the left indication that the reaction is ________.

• Most of the limiting reactant is not used.

HCN(aq) + H2O(l) H3O+(aq) + CN-(aq)HCN(aq) + H2O(l) H3O+(aq) + CN-(aq)

Reversible Reactions

• Acetic acid/H2O reaction

• HCl/H2O reaction

• Al(NO3)3/NaOH reaction

Acids and Bases

• Most acids are weak.– ______ acids are almost always weak.

• The O-H bond is broken.

• Demonstration with acetic acid, CH3COOH (show model).

• Write the reaction for the following acids with water.– HI, H2SO4, and (COOH)2

Acids and Bases

• A base is a substance the produces____ ions in aqueous solutions. The ___ ions produced, the stronger the base. Know the strong bases in Table 4-7.

• Generation of OH- ions in aqueous solutions– Dissociation of metallic hydroxides

– These dissolve and dissociate in water.

– What do the arrows indicate in the reaction?

NaOH(s) Na+(aq) + OH-(aq)H2O

NaOH(s) Na+(aq) + OH-(aq)NaOH(s) Na+(aq) + OH-(aq)H2O

Acids and Bases

• Generation of OH- ions in aqueous solutions– Bases that ionize in water

NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

– These substances ionize in order to produce OH-

• Mostly molecular substances

– Most molecular substances that ionize to produce OH- are weak bases.

– What do the arrows indicate about the limiting reactant?

Acids and Bases

• Some ionic hydroxides are essentially insoluble in water.

Cu(OH)2 CuOH+ + OH-

– Only a small amount of OH- ions are generated due to solubility.

DEMO: NaOH, NH3, and an insoluble hydroxide in water. Classify these bases.

Acids and Bases – A Summary

• Strong acids and bases– The substance largely dissolves or reacts to produce ions

(H3O+ or OH-)• Very small amount of limiting reactant remaining

– Large arrow points toward the product side.

• Weak acids and bases– Very small amount of the substance dissolves or reacts with

water to produce ions (H3O+ or OH-)• Large amount of limiting reactant remaining

– Large arrow points toward the reactant side

Determining if a Compound is Soluble

• Compounds whose solubility in water is less than 0.02 mol/L are generally classified as _______.– DEMO: Mg(OH)2 and NaCl

• Most substance are not infinitely soluble.– There is a limit to how much solid will dissolve

in water.



• Determine if the below compounds are soluble in water.– K2SO4, PbCl2, MgCO3, and NaOH

– Acids and bases that ionize or dissociate only slightly can still be soluble in water.

• CH3COOH and HF

You do not have to memorize the solubility rules. Make sure, however, that you can use the table.

Bonding, Solubility, Electrolyte Characteristics, and Predominant Forms of Solute in Water

Acids Bases Salts

Strong acids

Weak acids Strong bases Insoluble bases

Weak bases Soluble salts

Insoluble salts

Examples HCl HNO3

CH3COOH HF

NaOH Ca(OH)2

Mg(OH)2

Al(OH)3

NH3 CH3NH2

KCl NaNO3

BaSO4 AgCl

Ionic or molecular compound

Molecular Molecular Ionic Ionic Molecular Ionic Ionic

Solubility in water Soluble Soluble Soluble Insoluble Soluble Soluble Insoluble

Magnitude of dissociation or ionization in dilute aqueous solutions

Mostly ionized

Small amount of ionization

Mostly dissociated or ionized

Small amount of dissociation


Mostly dissociated


Solute mostly present Separate ions

Original acid

Separate ions Original base

Original base

Separate ions

Original salt

Arrows in chemical equation

Reactant- or product-favored

Product-favored

Reactant-favored

Product-favored

Reactant-favored

Reactant-favored

Product-favored

Reactant-favored

Reaction in Aqueous Solutions

• Formation of insoluble ionic compounds– Pb(NO3)2(aq) + NaI(aq) ?????

– Will a solid compound form? How can you determine this??

– Refer back to the solubility rules. Is there a combination that would be insoluble?

– Al(NO3)3(aq) + NaOH(aq) ?????

– NaCl(aq) + Ni(NO3)2(aq) ?????

Representing the Reactions in Aqueous Solutions

• Formula unit equations– All complete formulas are shown

2AgNO3(aq) + Cu(s) 2Ag(s) + Cu(NO3)2(aq)DEMO: ReactionWrite the formula unit equations for the previous reactions

• Total ionic equations– Formulas illustrate the predominant form that is present in the aqueous

solutions.• All species are still present.

2Ag+(aq) + 2NO3-(aq) + Cu(s) 2Ag(s) + Cu2+(aq) + 2NO3

-(aq)Write the total ionic equations for the previous reactions

Representing the Reactions in Aqueous Solutions

• Net ionic equations– Only the species that react (i.e. change) are

shown. Eliminate ions that don’t react. These are termed as spectator ions.

2Ag+(aq) + Cu(s) 2Ag(s) + Cu2+(aq)

Write the net ionic equations for the reactions done previously.

Oxidation Numbers

• Reactions that involve the formation of ionic compounds include the transfer of electrons– NaCl and CaBr2

– For these ionic compounds, oxidation numbers are used to keep track of electron transfers.

– The oxidation number (or oxidation state) of the ions in these compounds is simply the charge on the respective ion.

• NaCl and CaBr2

Oxidation Numbers

• In molecular compounds, oxidation numbers are also assigned in order to aid in writing formulas and balancing equations.– Oxidation numbers are assigned on a per atom

basis– Treat the rules in order of decreasing

importance

Page 138 (rules 1-8)

Useful Rules in Assigning Oxidation Numbers

• The oxidation number of any free, uncombined element is zero

• The oxidation number of an element in a simple (monatomic) ion is the charge on the ion

• In the formula for any compound, the sum of the oxidation numbers of all elements in the compound is zero. In a polyatomic ion, the sum of the oxidation numbers of the constituent elements is equal to the charge on the ion

Table 4-10

Assigning Oxidation Numbers

• NaNO3

• K2Sn(OH)6

• H3PO4

• SO32-

• Cr2O72-

Naming Binary Ionic CompoundsIUPAC

• Generally a metal combines with a nonmetal– Less electronegative element first

• Use element’s full name

– More electronegative element second• Stem (drop last part) and add ‘ide’

– Name the following ionic compoundsLiBr, MgCl2, and Al2O3

– Indicate the charge on metals that can have multiple charge states (transition metals and Groups IIIA (except Al), IVA, and VA)

• SnO, SnO2, and FeBr3

Naming Ionic Compounds with Polyatomic Ions

• Naming is very similar to the binary ionic compounds

• The polyatomic ion charge and name is taken from Table 2-3 and Table 4-11.

• Name the following ionic compounds– Al2(SO4)3, Ca(NO3)2, and (NH4)2SO4

Naming Binary Molecular Compounds

• Nonmetal bonded to a nonmetal– The first element listed (most metallic) is

named first • Receives full name.

– The second element listed in the formula is named second

• Drop the last portion of the name and add ‘ide’

– Relative amounts of each element is indicated by a prefix

• 2 – di, 3 – tri, 4 – tetra, 5 – penta, 6 – hexa

Naming Binary Molecular Compounds

• Let’s name some binary molecular compounds• SO3, OF2, and P4O6

• The minimum number of prefixes are used to name the compound unambiguously– mono, as a prefix, is not used

• Exception is CO, carbon monoxide

• The final ‘a’ in a prefix is omitted when the element begins with ‘o’– As4O6

Naming Binary Acids• Compounds in which H is bonded to a

Group VIA element other than O or to a Group VIIA element

• The pure compounds are named as typical binary compounds

• Aqueous solutions of the compounds are named by adding ‘hydro’ as a prefix and ‘ic’ as a suffix.– For the suffix, ‘ic’ the last portion of the

element is dropped

Naming Binary Acids

Compound Name of pure substance

Name in aqueous solution

HF Hydrogen fluoride

Hydrofluoric acid

HCl Hydrogen chloride

Hydrochloric acid

H2S Hydrogen sulfide

Hydrosulfuric acid

HBr Hydrogen bromide

Hydrobromic acid

Naming Ternary Acids

• The acids are composed of H, O, and one more element (usually a nonmetal)– H2SO4

– The ternary acids differ in the ____ of oxygen atoms contained in the acid

– H2SO4 and H2SO3

– The nonmetal must be able to have more than one oxidation state• Two of the acids are chosen as a basis (reference)

– The acid with the higher oxidation state number on the nonmetal or higher number oxygen atoms has a suffix ‘ic’

– The acid with the lower oxidation state on the nonmetal or smaller number of oxygen atoms has a suffix ‘ous’


Formula Oxidation State

Name Name Oxidation State

Name

HNO2 HNO3

H2SO4

H2SeO3


• Ternary acids that have one less O atom than the ‘ous’ acid is formed by adding the prefix ‘hypo’ and the suffix ‘ous’– H3PO2 – hyposphosporous acid

• What is the charge on the phosporus?

– Name HClO and determine the charge on Cl• HClO3 is chloric acid and HClO2 is chlorous acid


• Acids containing one more oxygen atom than the ‘ic’ acid are named by adding ‘per’ as a prefix and ‘ic’ as a suffix– HClO4 – perchloric acid

– Name HIO4 and determine the oxidation state on I

• HIO3 is iodic acid

Naming Ternary Salts

• These compounds are formed by replacing the hydrogen in a ternary acid with another ion that is usually a metal cation (occasionally NH4

+)– If the ternary acid ended in ‘ic’, the ‘ic’ is replaced

with ‘ate’– If the ternary acid ended in ‘ous’, the ‘ous’ is

replaced with ‘ite’– The ‘per’ and ‘hypo’ prefixes are retained with the

salts


Formula Name Formula Name

HClO Hypochlorous acid

NaClO Sodium hypochlorite

HClO2 Chlorous acid NaClO2 Sodium chlorite

HClO3 Chloric acid NaClO3 Sodium chlorate

HClO4 Perchloric acid NaClO4 Sodium perchlorate


• Hydrogen is included in naming the salts and the ions

• Name the following ternary salts and ions– NaHSO4 and KH2PO4

– H2PO2-1 and SO4

-2

• Page 145

Naming Ternary Acids and Salts

• Page 145, Problem-Solving Tip

Problems

Redox Reactions

• If there is a change in the oxidation number of an element in the reaction, the reaction can be classified as redox.– 4Al(s) + 3O2(g) 2Al2O3(s)

Assign oxidation states to all atoms.

Which element gained a greater oxidation state and which element gained a lower oxidation state?

Redox Reactions• Oxidation – an ______ in oxidation state or apparent

____ of electrons.• Reduction – a ______ in oxidation state or apparent

____ of electrons.Oxidation and reduction occur _________ in a reaction

(hence redox)• Oxidizing agents – species that oxidize other substances

– Gain electrons and are reduced

• Reducing agents – species that reduce other substances– Lose electron and are oxidized

Redox Reactions

• In the first reaction with Al and O2, identify the substances that are reduced and oxidized. Identify the oxidizing agent and reducing agent.

• 3Zn(s) + 2CoCl3(aq) 3ZnCl2(aq) + 2Co(s)

Is this a redox reaction? Write the net ionic equaiton. Identify oxidation states, the reduced and oxidized species, and the reducing and oxidizing agents.

Redox Reactions

• Al(NO3)3(aq) + 3NaOH(aq) Al(OH)3(s) + 3NaNO3(aq)

• 4KClO3(s) KCl(s) + KClO4(s)In the last reaction, the same element (Cl) is

oxidized and reduced. This is called a ______ reaction.

Obtain the information outlined in the previous slide for each reaction.

Combination Reaction

• In this type reaction, two simpler substances combine to form a compound of the combined simpler substances.– 2Mg(s) + O2(g) 2MgO(s)

– P4(s) + 10Cl2(g) 4PCl5(s)

– CaO(s) + CO2(g) CaCO3(s)

Which of these reactions is a redox? When combining _______ the reaction is always redox.

Decomposition Reactions

• In this type of reaction, a compound decomposed in simpler substances.– 2H2O(l) 2H2(g) + O2(g)

– 2KClO3(s) 2KCl(s) + 3O2(g)

– (NH4)2Cr2O7(s) Cr2O3(s) + 4H2O(g) + N2(g)

Determine which reactions are redox? If the reaction involves the formation of a ______, the reaction is always redox.

Displacement Reactions• In this reaction, one element displaces another

in a compound. These reactions are always _____.

2AgNO3(aq) + Cu(s) 2Ag(s) + Cu(NO3)2(aq)– Do you recall the total ionic and net ionic

equations?– This is a displacement reaction where a more active

metal displaces a less active metal in aqueous solution.

• More active metal + salt of less active metal Less active metal + salt of more active metal

Displacement Reactions

• The most active metals are on top of the column.– These tend to react to

become more ______.

• Elements at the bottom are least active.– These tend to become

or stay ______.


• Will the reactions proceed?

Cu(s) + Hg(NO3)2(aq) Cu(NO3)2(aq) + Hg(s)

Sn(s) + FeCl2(aq) SnCl2(aq) + Fe(s)

Write the net ionic equation for the reaction(s) that proceed? Is it redox?

Displacement Reaction

• If the metal is active enough, it may displace H2 from nonoxidizing acids such as HCl. In the reaction, the active metal becomes an aqueous salt.

Active metal + Nonoxidizing acid (most acids) Hydrogen gas + Salt of the acid

• Any metal above hydrogen in the activity series will displace H2 from the acid. – Look at table 4-12

2Al(s) + 3H2SO4(aq) 3H2(g) + Al2(SO4)3(aq)Write the net ionic equation.


• Will the below reactions proceed?

• Mg(s) + 2HCl(aq) H2(g) + MgCl2(aq)

• Cu(s) + H2SO4(aq) H2(g) + CuSO4(aq)

• Write the net ionic equation if the reaction proceeds.

DEMO:


• Which of the following metals will displace H2 from steam?– Co, Mg, and Sb

– Write the net ionic equation for the reaction that proceeds

• Which of the following metals will react with cold H2O(l) to displace hydrogen?– Na, Al, Cr

– Write the net ionic equation for the reaction that proceeds

Demo: Calcium


• If a group VIIA nonmetal is active enough it will react with less active group VIIA nonmetal present in a salt.– Cl2(g) + 2NaBr(aq) 2NaCl(aq) + Br2(g)

• Activity series for group VIIA – F2 > Cl2 > Br2 > I2

– The activity series progresses down the columnDEMO: Several reactions with gases and salts

Metathesis Reactions/Double Replacement

• Positive and negative ions appear to change ______ forming two new compounds– There is no change in _____ _____– Involves the removal of ____ in the reaction

• Driving force for the reaction

AX + BY AY + BX

Ag(NO3)aq + NaCl(aq) AgCl(s) + NaNO3(aq)Formula unit equation


• Three types of metathesis reactions– Formation of predominately nonionized

molecules in solution• Weak or nonelectrolytes (e.g. water)

– Formation of an insoluble solid• Insoluble precipitate

– Formation of a gas such as H2


• Formation of predominately nonionized molecules in solution– Many of these reactions are acid-base reactions

• Neutralization

– In nearly all these ‘neutralization’ reaction, H2O is the nonelectrolyte formed

• Formation of water is the driving force of the reaction

• Additionally, a soluble or an insoluble salt is formed– Cation of the base and anion of the acid

Acid/Base Reactions-A Metathesis Reaction

• Strong acid + strong base water + salt• Molecular equation

– HBr(aq) + KOH(aq) H2O(l) + KBr(aq)

• Total ionic equation– H+(aq) + Br-(aq) + K+(aq) + OH-(aq) H2O(l) + K+(aq)

+ Br-(aq)– H+ is an abbreviation that we will use for H3O+

• Net ionic equation– H+(aq) + OH-(aq) H2O(l)– This is the net ionic equation for all reactions between

strong acids and strong bases

Acid/Base Reactions-A Type of Metathesis Reaction

• Write the three equations for the below acid/base reaction.

2HNO3(aq) + Ca(OH)2(aq)Ca(NO3)2(aq) + 2H2O(l)

Acid/Base Reactions-A Type of Metathesis Reaction

• Reactions of weak acids with strong bases– CH3COOH(aq) + KOH(aq) KCH3COO(aq) +

H2O(l)

What are the total ionic and net ionic equations?

Note: The weak acids are only slightly ionized

General representation for this type of reaction;

HA(aq) + OH-(aq) A-(aq) + H2O(l)

Precipitation Reaction-A Type of Metathesis Reaction

• Formation of an insoluble solid

• Use the solubility guidelines covered previously to determine if an insoluble ionic compound will form– Pb(NO3)2(aq) + K3PO4(aq) ???

• Write the total and net ionic equations

Precipitation Reaction-A Type of Metathesis Reaction

• KCl(aq) + CaSO4(aq) ????

• HgCl2(aq) + KI(aq) ?????

Write the total ionic and net ionic for equations that proceed

Gas-Formation Reactions-A Type of Metathesis Reaction

• Gas formation is the driving force for this type of reaction

• 2HCl(aq) + CaCO3(s) H2CO3(aq) + CaCl2(aq)– Total ionic and net ionic equations (but wait)

– H2CO3(aq) dissociates

• H2CO3(aq) CO2(g) + H2O(l)

• Most of the gas evolves

• Total ionic and net ionic equations

DEMO: Limiting reactant and CO2 production

What should be left in the reaction beaker?

Gas-Formation Reactions-A Type of Metathesis Reaction

• MnS(s) + 2HCl(aq) H2S(g) + MnCl2(aq)

– H2S is rotten egg gas

Summary of Reaction Types

• Table 4-16

• You have to know how to classify the type of reaction and indicate if it is redox

Practice

Documents

Chemical Reactions Chapter 4. The Periodic Table Review –Arrangement is based on increasing ____ ____. –Groups or columns Elements within a group have

Chemical Reactions Chapter 4. The Periodic Table Review –Arrangement is based on increasing . –Groups or columns Elements within a group have