Common Types of Reactions
Jan 13, 2016
Common Types of Reactions
Combination Rxns Between non-metals to give a molecular product
Between metal and non-metal to yield an ionic product
Between compounds
N2(g) + O2 (g) 2NO(g)
4Al(s) + 3O2 (g) 2Al2O3(s)
NH3(g) + HCl(g) NH4Cl(s)
(Al3+, O2-)
Decomposition Rxns
CuSO4.5H2O(s) CuSO4(s) + 5H2O(g)
MgCO3(s) MgO(s) + CO2(g)
Single Replacement Rxns
Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)
Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)
Double Replacement (Metathesis) Rxns
Precipitation Reactions
Acid-Base (Neutralization) Reactions
HNO3(aq) + NaOH(aq) H2O(l) + NaNO3(aq) acid base salt
Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq)yellow solid
Acid-Base (Neutralization) Rxns
Oxidation-Reduction(Redox, Electron Transfer) Rxns
Precipitation Rxns
HNO3(aq) + NaOH(aq) H2O(l) + NaNO3(aq)
Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)
Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq)
More Than One Way to Categorize
More About Acids and Bases... Acids
Taste sour (vinegar, lemon juice) Turn litmus red React with bases to make H2O React with many metals to make H2
React with carbonates to make CO2 and H2O
Bases Taste bitter Turn litmus blue React with acids to make water Feel slippery
The Arrhenius View
Acid - yields H+ when added to water HCl(g) + H2O(l) H+(aq) + Cl- (aq)
unbalanced
Base - yields OH- when added to water NaOH(s) + H2O(l) Na+(aq) + OH-(aq)
unbalanced
Arrhenius View of Neutralization
acid + base a salt + water
HCl (aq) + NaOH (aq) NaCl (aq) + H2O
The Brønsted View More general approach, not limited to water
Brønsted acid = H+ donor Brønsted base = H+ acceptor
Neutralization = “proton” (H+) transfer
Why is HCl a Brønsted Acid?
hydronium ion, H3O+
acidbase
Why is Ammonia a Brønsted Base?
Redoxe- transfer rxns
Oxidation-Reduction
2Fe (s) + 3Cl2 (g) 2FeCl3 (s)Fe3+, Cl-
Fe is oxidized (loses e-): Fe Fe3+ + 3e-
Cl2 is reduced (gains e-): Cl2 + 2e- 2Cl-
reducing agent (supplier of e-): Feoxidizing agent (acceptor of e-): Cl2
Adding Half Rxns Yields Overall Rxn
3Cl2 + 6e- 6Cl-reduction
2Fe 2Fe3+ + 6e-oxidation
2Fe + 3Cl2 2FeCl3 overall
Problem: What is the oxidizing agent when copper reacts with silver nitrate to form silver and copper(II) nitrate?
Cu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s)
Ag+ is the oxidizing agent (consumes electrons from Cu)
Ag+ + 1e- Ag
Cu Cu2+ + 2e-
Problem: Is Cl reduced or oxidized when KClO3 decomposes?
2KClO3 2KCl + 3O2
?
Tracking e- Transfers
Oxidation State (Oxidation Number):The charge an element carries either alone or when
combined with other elements in a compound.
oxidation: O# goes upreduction: O# goes down
change in O# tells whether ox or red occurs
Simple Oxidation Number Rules
1. Free element O# = zero.Fe, Cl2, Na, Pb, H2, O2, P4 = 0
2. In monatomic ions, the O# = ion charge
Li+, Li = +1; Fe3+, Fe = +3; O2-, O = -2
3. Certain elements have same O# in ~all their compounds.
O usually -2, H usually +1 ...
4. (O# in cmpd) = overall charge of cmpd/ion.
More extensive rules are in text...
Problem: Is Cl reduced or oxidized when KClO3 decomposes ?
2KClO3 2KCl + 3O2
2KClO3 2KCl + 3O2
+1 -2 +1 -1 0+5Oxidation number drops (+5 to -1), so Cl is reduced.
1 potassium + 1 chlorine + 3 oxygens = 0 charge on KClO3
1(+1) + 1(?) + 3(-2) = 0
? = +5
HCO3-
1(+1) + 1(?) + 3x(-2) = -1
? = O# of C = +4
Problem: What are the oxidation numbers of all the elements in HCO3
- ?
O = -2
H = +1O#’s according to rules
C = ? no simple rule
1 hydrogen + 1 carbon + 3 oxygens = -1 charge anion
The Activity Series for Metals
Not important to memorize any of this. You’ll see it
again next semester.
Net Ionic Equations
To Describe Pptn and A-B Rxns
Problem: Pb(NO3)2 and NaCl ?
NaCl solution: contains Na+(aq) + Cl-(aq)
Pb(NO3)2 solution: contains Pb2+(aq) + NO3
-(aq)
How do we know ions are separated?
Problem: Pb(NO3)2 and NaCl ?
New Combinations?
Na+ with NO3-
NaNO3 is a strong electrolyte ions stay separated Represent as “NaNO3(aq)” or “Na+(aq) + NO3
- (aq)”
Pb2+ with Cl- PbCl2 is a weak electrolyte ions mostly together
Represent as “PbCl2(s)”
Ionic equation shows ions in correct state
Net ionic equation excludes spectator ions
2Na+ (aq) + 2Cl-(aq) + Pb2+(aq) + 2NO3-(aq)
--> PbCl2(s) + 2Na+ (aq) + 2NO3-(aq)
Pb2+(aq) + 2Cl-(aq) --> PbCl2(s)
Problem: Pb(NO3)2 and NaCl ?
Summary
Whole formula equation
Ionic equation
Net ionic equationPb2+(aq) + 2Cl-(aq) PbCl2(s)
2NaCl(aq) + Pb(NO3)2(aq) PbCl2(s) + 2NaNO3(aq)
2Na+ (aq) + 2Cl-(aq) + Pb2+(aq) + 2NO3-(aq)
PbCl2(s) + 2Na+ (aq) + 2NO3-(aq)
Problem: Write the net ionic equation for the reaction of sodium hydroxide and acetic acid in water.
wholeformula
ionic eqn
net ionic eqn
NaOH(aq) + HC2H3O2(aq) NaC2H3O2(aq) + H2O(l)
OH- + HC2H3O2 C2H3O2
- + H2O (l)
Na+ + OH-
+ HC2H3O2 Na+ + C2H3O2- + H2O
strong electrolyte
weak electrolyte
strong electrolyte
weak/non- electrolyte
wholeformula
ionic eqn
net ionic eqn
Problem: Write the net ionic equation for the reaction of sodium hydroxide and acetic acid in water.
Ca2+ + CO32- CaCO3
NH3 + H+ NH4+
Zn + 2HCl ZnCl2 + H2
Ca + F2 CaF2
Precipitation
Acid-Base
Redox (Single Displacement)
Redox (Combination)
Problem: Classify the following reactions.