Chemical Reactions
Download
Report
Transcript Chemical Reactions
Chapter 10
Reactions & Equations
Chemical Reaction
Process where the atoms of 1 or more substances are
rearranged to form different substances
Evidence for chemical rxns
Temp. change
Color change
Odor
Gas bubbles
Change in other appearance
Reactions & Equations
Use chemical equations to represent rxns
Reactants: Starting substances
Products: Substances formed during the rxn
Chemical eq. show direction of rxn
Reactant 1 + Reactant 2 -> Product 1 + Product 2
Symbols are used to show physical states
g = gas, s = solid, l = liquid, aq = aqueous (something
dissolved in water)
Reactions & Equations
Word Equations
Iron (s) + chlorine (g) -> iron (III) chloride (s)
Iron and chlorine react to form iron (III) chloride
Skeleton Equations
Uses chemical formulas
Fe (s) + Cl2 (s) -> FeCl3 (s)
Write the skeleton eq for the rxn between carbon & sulfur to
form carbon disulfide
Write the chemical formula for reactants
Write the chemical formula for products
C (s) + S (s) -> CS2 (l)
Practice Probs
Write the skeleton equations for the following:
Hydrogen (g) + Bromine (g) -> Hydrobromic acid (g)
H2 (g) + Br2 (g) -> HBr (g)
Carbon monoxide (g) + Oxygen (g) -> Carbon dioxide
CO (g) + O2 (g) -> CO2
Reactions & Equations
Balancing Chemical Equations
Chemical eq must show the conservation of mass (in this case
atoms)
For example:
2Fe (s) + 3Cl2 (g) -> 2FeCl3 (s)
2 Fe atoms on each side
6 Cl atoms on each side
The #’s in front of reactant/product is called a coefficient
(the # written in front of a reactant or product)
Reactants/products w/out a coefficient have a coefficient of 1
Reactions & Equations
Balance: Hydrogen and chlorine react to form hydrochloric acid
Steps for Balancing Equations:
Write the skeleton equation
H2 (g) + Cl2 (g) -> HCl (g)
Count the atoms of the elements in reactants & products
Reactants: 2 H
2 Cl
Products: 1 H
1 Cl
Change the coefficients to make the # atoms on each side equal (guess & check)
H2 (g) + Cl2 (g) -> 2HCl (g)
Write the coefficients in their lowest possible ratio (simplify if possible)
Simplified
CHECK YOUR WORK!
Practice Probs
Write balanced chemical equations:
Iron (III) chloride reacts w/sodium hydroxide,
producing solid iron (III) hydroxide and sodium
chloride
Practice Probs
Write balanced chemical equations:
Liquid carbon disulfide reacts w/oxygen gas,
producing carbon dioxide gas and sulfur dioxide gas
Practice Probs
Write balanced chemical equations:
Solid zinc and aqueous hydrogen sulfate react to
produce hydrogen gas and aqueous zinc sulfate
HOMEWORK
Pg. 283 #7-13
Pg. 304 # 71-78
Classifying Chemical Reactions
Synthesis Reactions
A chemical rxn where 2 or more substances react to produce a
single reaction
A + B = AB
Fe (s) + Cl2 (g) FeCl3
Sodium and chlorine react to produce sodium chloride
Calcium oxide and water combine to form calcium hydroxide
Sulfur dioxide gas reacts w/oxygen gas to form sulfur trioxide
Classifying Chemical Reactions
Combustion Reactions
Oxygen combines w/a substance & releases energy (heat
& light)
Hydrogen & oxygen gas is heated to form water
Rxn between solid carbon & oxygen gas to form carbon
dioxide & water
Methane gas reacts w/ oxygen gas to form carbon
dioxide & water
Practice Prob 4
The solids aluminum and sulfur react to produce
aluminum sulfide
Practice Prob 5
Water and dinitrogen pentoxide gas react to produce
aqueous hydrogen nitrate
Practice Prob 6
The gases nitrogen dioxide and oxygen react to
produce dinitrogen pentoxide gas.
Practice Prob 7
Ethane gas (C2H6) burns in air producing carbon
dioxide and water vapor.
Classifying Chemical Reactions
Decomposition Reactions
Single compound breaks down into 2 or more
substances
AB A + B
Ammonium nitrate breaks down into dinitrogen
monoxide & water
Sodium azide (NaN3) breaks down into sodium solid &
nitrogen gas. (Air bags)
Practice Prob 8
Aluminum oxide (s) decomposes when electricity is
passed through it.
Practice Prob 9
Nickel (II) hydroxide (s) decomposes to produce nickel
(II) oxide (s) and water.
Classifying Chemical Reactions
Single-Replacement Reactions
Atoms of 1 element replace the atoms of another
element in a compound
A + BX AX + B
Lithium (s) and water (l) react to form lithium
hydroxide (aq) and hydrogen (g)
Copper (s) and silver nitrate (aq) react to form silver (s)
and copper nitrate (aq)
Practice Prob 10
Predict if the following single-replacement rxn will
occur:
K (s) + ZnCl2 (aq)
Practice Prob 11
Predict if the following single-replacement rxn will
occur:
Cl2 (g) + HF (aq)
Practice Prob 12
Predict if the following single-replacement rxn will
occur:
Fe (s) + Na3PO4 (aq)
Classifying Chemical Reactions
Double-Replacement Reactions:
Exchange of ions between 2 compounds
AX + BY AY + BX
Ca(OH)2 (aq) + 2HCl (aq) CaCl2 (aq) + 2H2O (l)
NaOH (aq) + CuCl2 (aq) NaCl (aq) + Cu(OH)2 (s)
Solid produced during a rxn is a precipitate
Classifying Chemical Reactions
Double-Replacement Reactions:
All produce either a precipitate, a gas, or water
KCN (aq) + HBr (aq)
Practice Prob 13
Aqueous lithium iodide and aqueous silver nitrate
react to produce solid silver iodide and aqueous
lithium nitrate
Practice Prob 14
Aqueous barium chloride and aqueous potassium
carbonate react to produce solid barium carbonate and
aqueous potassium chloride
HOMEWORK
Pg. 291 # 27-32
Aqueous Solutions
Solution contains 1 or more substances known as solutes
dissolved in another substance
Substance that does the dissolving the solvent
Aqueous Solution
Solvent is water
Many different solutes
HCl (g) H+ (aq) + Cl- (aq)
NaOH (aq) Na+ (aq) + OH- (aq)
Ions in the solution may react w/other ions in solution
Double-replacement reaction
Aqueous Solutions
Reactions that form precipitates
2NaOH (aq) + CuCl2 (aq) 2NaCl (aq) + CuOH (s)
Double-replacement rxn
Complete Ionic Equation
2 Na+ (aq) + 2OH- (aq) + Cu2+ (aq) + 2Cl- (aq) 2Na+ (aq) + 2Cl- (aq) + Cu(OH)2 (s)
Aqueous means they are in solution of water & are present as
ions
Spectator Ions: Ions that do not participate in the rxn & are
found in both the reactants & products
Na+ & Cl Net Ionic Equations: eliminate spectator ions
2OH- (aq) + Cu2+ (aq) Cu(OH)2 (s)
Practice Prob 15
Write the chemical, complete ionic, and net ionic
equations:
Aqueous solutions of potassium iodide & silver nitrate
are mixed forming the precipitate silver iodide.
Practice Prob 16
Write the chemical, complete ionic, and net ionic
equations:
Aqueous solutions of ammonium phosphate & sodium
sulfate are mixed. No precipitate forms and no gas is
produced.
Practice Prob 17
Write the chemical, complete ionic, and net ionic
equations:
Aqueous solutions of aluminum chloride and sodium
hydroxide are mixed, forming the precipitate aluminum
hydroxide.
Reactions that Form Water
Since water is formed, you cannot tell if a rxn has
occurred
HBr (aq) + NaOH (aq) H2) (l) + NaBr (aq)
Reactants & product remain in solution
Complete ionic equation:
H+ (aq) + Br- (aq) + Na+ (aq) + OH- (aq) H2O (l) + Na+ (aq) + Br- (aq)
Reacting ions are H+ & OH-
Net Ionic Equation:
H+ (aq) + OH- (aq) H2O (l)
Practice Prob 18
Write Chemical, Complete Ionic, & Net Ionic
equations:
Sulfuric acid (H2SO4) & aqueous potassium hydroxide
Practice Prob 19
Write Chemical, Complete Ionic, & Net Ionic
equations:
Hydrochloric acid (HCl) & aqueous calcium hydroxide
Reactions That Form Gases
Some double-replacement rxns form gases
Carbon dioxide, hydrogen cyanide, hydrogen sulfide, & hydrogen
are common
Chemical Equation:
2HI (aq) + Li2S (aq) H2S (g) + 2LiI (aq)
Complete Ionic Equation:
2H+ (aq) + 2I- (aq) + 2Li+ (aq) + S2- (aq) H2S (g) + 2Li+ (aq) + 2I- (aq)
Net Ionic:
2H+ (aq) + S2- (aq) H2S (g)
HOMEWORK
Pg. 294 # 36-37;
Pg. 296 # 40-42;
Pg. 299 # 43-51