chapter 11 chemical reactions hingham high school mr. dan clune
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All chemical reactions• Two parts:
• – what you start with
• what you end with• Reactants turn into the products.• Reactants ® Products
In a chemical reaction• Can be described several ways:1. In a sentence
Copper with chlorine to copper (II) chloride.
2. In a word equation
Copper + chlorine ® copper (II) chloride
Symbols in equations-p.323
• () separates reactants from products
• Read “reacts ”• Plus (+) sign read “ ”
Cu + Cl2 CuCl2
Symbols used in equations
• (s) = • (g) = • (l) = • (aq) - dissolved in water,
an solution.
Cu(s) + Cl2(g) CuCl2(s)
Symbols used in equations
•↑ after product, indicates produced
•same as (g) - H2↑•¯after product, indicates
produced •same as (s) - PbI2↓
Symbols used in equations
indicates reaction
shows that is supplied to the reaction
is - indicates a is supplied, in this case, platinum.
heat ,
Pt
What is a catalyst?
• up a reaction• Is NOT or
by the reaction.• Enzymes are biological or protein
catalysts.
Convert this to an equation
• Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form iron (III) chloride and hydrogen sulfide gas.
Nitric acid dissolved in water reacts with solid sodium carbonate to form liquid water, carbon dioxide gas, sodium nitrate dissolved in water.
Now, read these:
• Fe(s) + O2(g) ® Fe2O3(s)
• Cu(s) + AgNO3(aq) ® Ag(s) + Cu(NO3)2(aq)
• NO2 (g) N2(g) + O2(g) Pt
Balanced Equation• Atoms can’t be created or destroyed• All the atoms we with
we must up with• A balanced equation has the
of each element on of the equation.
• C + O2 ® CO• Need one more O in the .• Can’t change the ,
because it describes what it is (carbon monoxide in this example)
C + O® COO
Finding the number of atoms
• The subscript in front of an element is the number of atoms of that element / polyatomic.• Ex) CO2 B2(SO4)3
• C= O= B= SO4=
• A coefficient in front of the formula multiplies the amount of elements by the coefficient.• Ex) 3CO2 2B2(SO4)3
• C= O= B= SO4=
Finding the number of atoms
H2O H= O=
2H2O H= O=
B(NO3)2 B= NO3=
3B(NO3)2 B= NO3=
Pb3(PO4)4 Pb= PO4=
2Pb3(PO4)4 Pb= PO4=
Rules for balancing:3. Count the of atoms
of each appearing on sides of the equation.
4. Balance the elements one at a time by adding (the numbers in front)-Save and until LAST!
Rules for balancing:
5. Check to make sure it is balanced.
6. Make sure the coefficients are in the possible ratio.
Don’t you ever…
• Never change a to balance an equation.• H2O is a different compound than H2O2
• Never put a coefficient in the of a formula
• 2 NaCl is okay, Na2Cl is not. X
Section 8.2Types of Chemical Reactions
• OBJECTIVES:• Identify a reaction as combination,
decomposition, single-replacement, double-replacement, or combustion
Types of Reactions• 5 major types.• predict the products• predict whether or not they will happen at all
• How? We recognize them by their
#1 - Combination Reactions• Combine - put together• substances combine to
make one .
A + B ®AB• Ca +O2 ®CaO
• SO3 + H2O ® H2SO4
Write and balance
• Ca + Cl2 ®
• Fe + O2 ® iron (II) oxide
• Al + O2 ®• Remember that the first step is to write
the correct formulas• Then balance by using only
#2 - Decomposition Reactions• Decompose = fall apart• reactant falls apart into
elements or compounds.
AB A + B
#2 - Decomposition Reactions
•NaCl Na + Cl2
•CaCO3 CaO + CO2
•Note that is usually required to decompose
electricity
#2 - Decomposition Reactions• Binary compounds (made of 2 elements)
falls apart into its elements
• H2O
• HgO
electricity
#3 - Single Replacement Reactions• element
another (new dance partner)
• Reactants are an • Products will be a
element and different cmpd• Li + KCl ® K + LiCl
• F2 +2 LiCl ® 2LiF + Cl2
(Cations switched)
(Anions switched)
#3 Single Replacement Reactions• Metals replace other metals (and H)• K + AlN ®• Zn + HCl ® • Think of water as: HOH
• Metals replace first H, then combines w/ hydroxide (OH).
• Na + H2O ®
#3 Single Replacement Reactions• Sometimes, the reaction will happen:
Some chemicals are more “ ” than others• active replaces
active
The “Activity Series” of Metals• Lithium• Potassium• Calcium• Sodium• Magnesium• Aluminum• Zinc• Chromium• Iron• Nickel• Lead• Hydrogen• Bismuth• Copper• Mercury• Silver• Platinum• Gold
If the lone metal is the paired metal, replacement occur.
Ex) Li + NaCl ® Na + LiCl
If the lone metal is the paired metal, replacement will occur.
Ex) Na + LiCl ® Na + LiCl
Higher activity
Lower activity
The “Activity Series” of Halogens
Fluorine Chlorine Bromine Iodine
If the lone halogen is the paired
halogen, replacement occur.
2NaCl(s) + F2(g)
MgCl2(s) + Br2(g)
Higher Activity
Lower Activity
#3 Single Replacement Reactions Practice:
• Fe + CuSO4 ®
• Pb + KCl ®
• Al + HCl ®
• Lithium• Potassium• Calcium• Sodium• Magnesium• Aluminum• Zinc• Chromium• Iron• Nickel• Lead• Hydrogen• Bismuth• Copper• Mercury• Silver• Platinum• Gold
Higher activity
Lower activity
#4 - Double Replacement Reactions• things each
other.• Reactants must be two
compounds.
• NaOH + FeCl3 ®• positive ions change place
• NaOH + FeCl3 ®Fe+3 OH- + Na+1 Cl-1
=
Complete and balance:
• assume all of the following reactions actually take place:CaCl2 + NaOH ®
CuCl2 + K2S ®
KOH + Fe(NO3)3 ®
K2SO4 + BaF2 ®
How to recognize which type?• Look at the reactants:
El + El = Combination
Cpd = Decomposition
El + Cpd = Single replacement
Cpd + Cpd = Double replacement
Practice Examples:• H2 + O2 ®
• H2O ®
• Zn + H2SO4 ®• HgO ® • KBr + Cl2 ®
• AgNO3 + NaCl ®
• Mg(OH)2 + H2SO3 ®
#5 – Combustion Reactions• Combustion means “ ”• Normally, a cpd composed of only C, H,
(sometimes O) is reacted with oxygen – called “burning”
• combustion, products are
SUMMARY: An equation...• Describes a rxn• Must be • only balance by changing
• special symbols to indicate physical state, catalyst or energy required, etc.
Reactions• 5 major types• We can tell what type they are by looking at
• Single Replacement happens based on the Series
Net Ionic Equations• Many reactions occur in water,
or solution• When dissolved in water, many ionic
cpds “dissociate”, or ,into cations & anions
• Now write ionic equation
Net Ionic Equations• Example (needs to be a double replacement reaction)
AgNO3 + NaCl AgCl + NaNO3
1. this is the full balanced equation2. next, write it as ionic equation by splitting
the cpds into their ions:Ag1+ + NO3
1- + Na1+ + Cl1-
AgCl(s) + Na1+ + NO31-
Solids do not split up.
Net Ionic Equations3. Crossing out ions that did not change
(called spectator ions)Ag1+ + Cl1- AgCl (s)
This is the
Predicting the Precipitate• Insoluble salt is a precipitate
• i.e. a solid• General solubility rules are found:
a) Table 11.3, p. 344 in textbook
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