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Precipitation Reactions. Example: Write the complete balanced molecular equation for the reaction between Na 3 PO 4 (aq) and CaCl 2 (aq). Write the complete ionic equation and the net ionic equation for the reaction. Ions: Na + PO 4 3- Ca 2+ Cl -. Possible Products: NaCl - PowerPoint PPT Presentation
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Precipitation Reactions
Example: Write the complete balanced molecular equation for the reaction between Na3PO4 (aq) and CaCl2 (aq). Write the complete ionic equation and the net ionic equation for the reaction.
Ions: Na+ PO43-
Ca2+ Cl-
Possible Products:
NaCl
Ca3(PO4)2
Precipitation Reactions
Solubilities:
NaCl
Ca3(PO4)2
soluble
insoluble
(aq)
(s)
Precipitation Reactions
Unbalanced Molecular Eq’n:
Na3PO4 (aq) + CaCl2 (aq) Ca3(PO4)2 (s) +NaCl (aq)
Balanced Molecular Eq’n:
2 Na3PO4 (aq) + 3 CaCl2 (aq) Ca3(PO4)2 (s) +6 NaCl (aq)
Precipitation Reactions
Complete Ionic Equation:
6 Na+ (aq) + 2PO43- (aq) + 3 Ca2+ (aq) + 6 Cl- (aq)
Ca3(PO4)2 (s) + 6 Na+ (aq) + 6 Cl- (aq)
Net Ionic Equation:
3 Ca2+ (aq) + 2 PO43- (aq) Ca3(PO4)2 (s)
Precipitation Reactions
Example: Write the equation for the reaction between NH4Cl (aq) and CaSO4 (aq).
Ions: NH4+ Cl-,
Ca2+ SO42-
Possible Products: (NH4)2SO4
CaCl2
Precipitation Reactions
Solubility of Products:
(NH4)2SO4
CaCl2
soluble
soluble
(aq)
(aq)
Precipitation Reactions
NH4Cl (aq) + CaSO4 (aq) No Reaction
If both products are soluble (aq), then NO REACTION is presumed to occur between the ionic compounds involved. The reaction mixture simple contains a
mixture of soluble ions.
On your exam, you should be able to indicate whether a reaction occurs or not. •If it occurs, write the formulas for the products and balance.•If no reaction occurs, write the words, “No Reaction”
Acids & Bases Acids:
substances that ionize in aqueous solution to form one or more hydrogen ions (H+)
increase the concentration of H+ ions in solution
Acids are sometimes called proton donors. H+ is often called a proton
Acids & Bases Examples of Acids:
HCl hydrochloric acid HNO3 nitric acid HC2H3O2 acetic acid H2SO4 sulfuric acid H3PO4 phosphoric acid
Note: Acids can form different numbers of H+ ions!
Acids & Bases Monoprotic acids
have one H in the formula form a single H+ ion when they ionize
HNO3 (aq) H+ (aq) + NO3- (aq)
Acids & Bases Diprotic acids
have two H’s in the formula can form two H+ ion when they ionize
completely
H2SO4 (aq) 2H+ (aq) + SO42- (aq)
Polyprotic acids: Have two or more H’s in the formula Form two or more H+ ions when they ionize
completely
Acids & Bases Bases:
substances that accept (react with) H+ ions. any substance that increases the OH-
concentration when added to water
Examples:
Hydroxide ion (OH-) OH- (aq) + H+ (aq) H2O (l)
Acids & Bases Examples (cont)
Common hydroxide containing bases: NaOH, KOH, Ca(OH)2
Note: These are strong electrolytes!
NaOH (aq) Na+ (aq) + OH- (aq)
Acids & Bases Examples (cont):
Ammonia (NH3) Does not contain OH-
Accepts H+ ion from water and increases the OH- concentration in the water
NH3(aq) + H2O (l) NH4+ (aq) + OH- (aq)
NH3 is a weak electrolyte!!
Acids & Bases Strong Acid:
an acid that is a strong electrolyte ionizes completely in solution
Weak Acid: an acid that is a weak electrolyte
an acid that does not ionize completely
Acids & Bases Strong acids:
Know the names and formulas of the 7 common strong acids:
HCl (aq) hydrochloric acid HBr (aq) hydrobromic acid HI (aq) hydroiodic acid HClO3 chloric acid HClO4 perchloric acid HNO3 nitric acid H2SO4 sulfuric acid
Acids & Bases Examples of Weak Acids
HF (aq) hydrofluoric acid H3PO4 phosphoric acid HC2H3O2 acetic acid
Acids & Bases Strong Base:
a base that is a strong electrolyte ionizes completely in solution
Weak Base: a base that is a weak electrolyte does not ionize completely in solution
Acids & Bases Strong Bases: Know the names and formulas
of the strong bases
Alkali metal (1A) hydroxides LiOH lithium hydroxide NaOH sodium hydroxide KOH potassium hydroxide RbOH rubidium hydroxide CsOH cesium hydroxide
Acids & Bases Strong bases to know (con’t):
Heavy alkaline earth metal (2A) hydroxides Ca(OH)2 calcium hydroxide Sr(OH)2 strontium hydroxide Ba(OH)2 barium hydroxide
Acids & Bases Examples of Weak Bases:
ammonia (NH3) sodium bicarbonate (NaHCO3)
baking soda a component of Alka-Seltzer
Acid-Base Reactions Reactions between acids and bases are called
neutralization reactions. The products of these reactions have very
different properties than the reactants.
HCl (aq) + NaOH (aq) H2O (l) + NaCl (aq)
Sharpsour
bitterslippery
salt
Acid-Base Reactions Salt:
any ionic compound whose cation comes from a base and whose anion comes from an acid
An ionic compound that is neither an acid nor a base
In general,
acid + metal hydroxide a salt + water
Acid-Base Reactions Neutralization reactions are a type of
metathesis reaction.
To predict the products: identify the ions present exchange anions write the correct formulas for the products write a balanced equation
Acid-Base Reactions
Example: Write the balanced equation for the reaction between HBr (aq) and Ca(OH)2 (aq).
Ions: H+ Br-
Ca2+ OH-
Possible Products:H-OH = H2O
CaBr2
2HBr (aq) + Ca(OH)2 (aq) CaBr2 (aq) + 2H2O (l)
Acid-Base Reactions Notice that you can also write complete and
net ionic equations for acid-base reactions:
Complete ionic equation:
2 H+ (aq) + 2Br- (aq) + Ca2+ (aq) + 2 OH- (aq) Ca2+ (aq) + 2 Br- (aq) + 2 H20 (l)
Molecular equation:
2HBr (aq) + Ca(OH)2 (aq) CaBr2 (aq) + 2H2O (l)
Acid-Base Reactions
Net ionic equation:
H+ (aq) + OH- (aq) H2O (l)
Note: This is the net ionic equation between any strong acid and strong base.
Complete ionic equation:
2 H+ (aq) + 2Br- (aq) + Ca2+ (aq) + 2 OH- (aq) Ca2+ (aq) + 2 Br- (aq) + 2 H20 (l)
Acid-Base Reactions
Example: Write the balanced equation for the reaction between Mg(OH)2 (s) and HCl (aq).
Ions: Mg2+ OH-
H+ Cl-
Products: MgCl2 (aq)
H-OH = H2O (l)
Acid-Base Reactions
Molecular Equation:Mg(OH)2 (s) + 2 HCl (aq) MgCl2 (aq) + 2 H2O (l)
Net ionic equation:Mg(OH)2 (s) + 2 H+ (aq) Mg2+ (aq) + 2 H2O (l)
Complete Ionic Equation:Mg(OH)2 (s) + 2 H+ (aq) + 2 Cl- (aq) Mg2+ (aq) +
2 Cl- (aq) + 2 H2O (l)
Acid-Base Reactions There are many bases that do not contain OH-
Na2S NaCN NaHCO3
These bases react with acids to form gaseous products.
Acid-Base Reactions
Examples:
Na2S (aq) + 2 HCl (aq) H2S (g) + 2 NaCl (aq)
HCl (aq) + NaHCO3 (aq) NaCl (aq) + H2CO3 (aq)
but:H2CO3 (aq) H2O (l) + CO2 (g)
so:
HCl (aq) + NaHCO3 (aq) NaCl (aq) + H2O (l) + CO2 (g)
Oxidation-Reduction Reactions Precipitation Reactions:
ions combine to form insoluble products
Neutralization Reactions: H+ ions and OH- ions combine to form H2O
Oxidation-Reduction (Redox) Reactions: Atoms or ions give or accept electrons
Redox Reactions Corrosion of your car
battery terminal is caused by a reaction between the metal terminal, oxygen, and the battery acid, H2SO4.
This reaction is a redox reaction.
Redox Reactions Oxidation-Reduction Reactions (Redox
Reactions) reactions that involve the transfer of
electrons between two reactants an element in one reactant is oxidized while
an element in another reactant is reduced
Mg (s) + 2 H+ (aq) Mg2+ (aq) + H2 (g)
oxidized reduced
Redox Reactions Oxidation:
the loss of electrons chemical species becomes more
positively charged
the gain of oxygen
the loss of hydrogen
Redox Reactions Reduction:
the gain of electrons the chemical species becomes more
negatively charged
the gain of hydrogen
the loss of oxygen
Redox Reactions LEO:
Lose Electrons Oxidation
GER:
Gain Electrons Reduction
GER
LEO
LEO says GER
Redox Reactions
Oil Rig
Oil : Oxidation Involves
Loss of e-
Rig : Reduction Involves
Gain of e-
Redox Reactions Electrons are not explicitly shown in
chemical equations.
Oxidation Numbers are used to keep track of electrons gained and lost during redox reactions.
Oxidation number a hypothetical number assigned to an
individual atom present in a compound using a set of rules.
May be positive, negative, or zero
Rules for Oxidation Numbers
Oxidation numbers are always reported for individual atoms or ions not groups of atoms or ions!!!!!!!!!!!
For an atom in its elemental form, the oxidation number is always zero.
H2: oxidation # = 0 for each H atom Cu: oxidation number = 0 Cl2: oxidation # = 0 for each Cl atom
Rules for Oxidation Numbers
For any monoatomic ion, oxidation # = charge on ion
K+ oxidation # = +1 Cl- oxidation # = -1 S2- oxidation # = -2
Rules for Oxidation Numbers
Group 1A Metal Cations: Always +1
Group 2A Metal Cations: Always +2
Hydrogen (H) +1 when bonded to nonmetals -1 when bonded to metals
Rules for Oxidation Numbers
Oxygen (O) -1 in peroxides (O2
2-) -2 in all other compounds
Fluorine (F) always -1
Rules for Oxidation Numbers
The sum of the oxidation numbers of all atoms in any chemical species (ion or neutral compound) is equal to the charge on that chemical species
H2O: 1 + 1 + -2 = 0
MgCl2: 2 + -1 + -1 = 0
MnO4- : 7 + -2 + -2 + -2 + -2 = -1
Oxidation Numbers For many compounds, you will be able to
directly apply the rules to determine the oxidation number of all atoms except for one. Use the last two rules to determine the
oxidation number of that last element.
Oxidation Numbers
Example: Determine the oxidation state of all elements in SO3.
Is it elemental?
Are any monoatomic ions present?
Which elements have rules?
Set up an equation to find the remaining oxidation number.
No
No
O = -2
S + 3(-2) = 0 S = +6
Oxidation Numbers
Example: Determine the oxidation number of Mn and O in MnO4
-.
Mn + 4(-2) = -1 so Mn = +7
Is it elemental?
Are any monoatomic ions present?
Which elements have rules?
Set up an equation to find the remaining oxidation number.
No
No
O = -2
Oxidation Numbers
Example: Determine the oxidation state of all elements in NaNO3
Is it elemental?
Are any monoatomic ions present?
Which elements have rules?
Set up an equation to find the remaining oxidation number.
No
Na+
Na = +1, O = -2
1 + N + 3(-2) = 0 N = +5
Oxidation Numbers
Example: Determine the oxidation number of P in HPO4
2-
Oxidation Numbers
Example: Determine the oxidation state of all elements in Cr2O7
2-.