Chemical Reactions and Equations Types of Reactions ...
Transcript of Chemical Reactions and Equations Types of Reactions ...
Chemical Reactions and Equations
Types of Reactions
Predicting Products
Activity Series
Identifying Oxidation-Reduction
Reactions
A preview of things we will do
Chemical Reactions are AWESOME!
Characteristics of Chemical Reactions
A chemical reaction: is a process in which the chemical and physicalproperties of the original substance changes
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and new substances with differentphysical and chemical properties are formed.
Chemical Equations
A chemical equation has two
parts:
• reactants: the starting materials
• products: the substances
formed in the reaction (ending)
example: C + O2 CO2reactants products
Identifying Reactants and Products
Identify the reactants and products in the following equation:
2Al(s) + 3Cl2(g) → 2AlCl3(s)
reactant(s)
products(s)
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Al, Cl2
AlCl3
Reaction SymbolsYields or Produces
Solid or precipitate (s) or
Liquid (l)
Gas (g) or
Aqueous (acids & bases) (aq)
Catalyst (speeds up) Ni
Heat Added
Reversible Reaction ⇄
Identifying parts of a Chemical Equation:
1. Which are the reactants?
2. Which are the products?
3. Which are the coefficients?
4. Which is the subscript?
2 Mg + O2 2 MgO
Reactants Products
Mg + O2
MgO
# in front
# on bottom
SRIRACHA!!!
Indications of a Chemical Reaction
1. Production of a gas.
2. Formation of a precipitate. (a solid that forms from two liquids)
3. Change in energy.
Endothermic reaction – energy is absorbed
Exothermic Reaction – energy is released
4. Change in color or odor.
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Why wet dogs stink!!!
Law of Conservation of Mass
Chemical equations are balanced to satisfy the Law of Conservation of Mass
The Law of Conservation of Mass states: mass cannot be created or destroyed by ordinary physical or chemical means.
total mass of the reactants must equal the total mass of the products.
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Law of Conservation of Mass
-Mass is neither created nor destroyed!
The number of atoms (and total mass) on the reactant side
must equal the number of atoms (and total mass) on the
product side.
1CH4 + 2O2 1CO2 + 2H2O16 g + 64 g = 44 g + 36 g
80 g = 80 g
Example: In a chemical reaction, 4 g of hydrogen combine with 32 g of oxygen to form water (2H2 + O2 2H2O). What is the mass of the product formed?
Answer: Reactants = Products
4 g + 32 g = 36 g H2O
Remember: Calculate formula mass.
(1 C x 12) + (4 H x 1) =
16 g
Practice:1. In a chemical reaction, 4 g of hydrogen combine with 32
g of oxygen to form water What is the mass of the product formed?
2H2 + O2 2H2O
2. If 60 g of ethane burns in 224 g of oxygen to produce 108 g
of water, what is the mass of the remaining product?
C2H6 + O2 CO2 + H2O
4 g + 32 g = ? g
60 g + 224 g = ? g + 108 g 176 g
36 g
Homework/Do NOW:
Conservation of Mass Practice Problems (12 questions)
Due FRIDAY 1/29/16
Turn it in today if you finish!
Warm-Up: Answer the following
1. What are the two parts of a chemical equation?
2. What is the law of conservation of mass?
3. According to the law, what must be equal on both sides of the equation? (hint: there are TWO things that must be equal (the total number of _______ and the total ________ in grams)
Law of Conservation of Mass
Remember that atoms don’t
change in a chemical reaction;
they just rearrange.
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For a chemical equation to accurately
represent a reaction, the same number of
each kind of atom must be on the left side of
the arrow as are on the right side.
Counting Atoms in Chemical Compounds
Before we can balance an equation, we must first make
sure that everyone can count the atoms present in a
compound. Here are some examples.
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KClO3 ___K, ___Cl, ___O
Mg(OH)2 ___Mg, ___O, ___H
Al2(SO4)3 ___Al, ___S, ___O
2Al(NO3)3 ___Al, ___N, ___O
1 1 3
1 2 2
2 3 12
2 6 18
You Try It
Determine the number of each atom present
in each of the following.
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AlPO3 ___Al, ___P, ___O
Ba(NO3)2 ___Ba, ___N, ___O
HC2H3O2 ___H, ___C, ___O
3Fe3(PO4)2 ___Fe, ___P, ___O
1 1 3
1 2 6
4 2 2
9 6 24
Identifying Balanced Chemical Equations
An equation in which the number of atoms of
each element is the same on both sides of
the equation is called a balanced chemical
equation.
Pb(NO3)2 + 2KI → PbI2 + 2KNO3
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Reactant Side Element Product Side
Pb
N
O
K
I
1 12 26 6
2 22 2
You try it: Handout
Balancing Practice I
Worksheet
15 minutes. GO!
Balancing Chemical Equations
Example:
Mg + HCl → MgCl2 + H2
What coefficient must be added in front of
HCl in order to balance the chlorine and the
hydrogen?
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2
Ex. 1: Mg + HCl MgCl2 + H2
Ex. 2: KClO3 − KCl + O2
1 Mg 1 Mg1 H 2 H
2
1 K
1 Cl
3 O
2
1 Cl
2
2 Cl
3
2 H
2 Cl
1 1 1
1 K
1 Cl
2 K
2 Cl
6 O
2 O2 K
2 Cl
6 O
Writing Balanced Chemical Equations
If the skeleton equation is not written for you,
you must write your own.
Example** When an electric current is passed
through water, the water molecules break
down to produce hydrogen and oxygen.
Bubbles of each gas are evidence of the
reaction.
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→ H2(g)H2O(l) + O2(g)2 2
You Try It
Write a balanced equation for each of the
following reactions.
**When magnesium metal and oxygen gas
react, the product is solid magnesium
oxide.
**When nitrogen and hydrogen gas react, the
product is ammonia gas.
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N2(g) + H2(g) → NH3(g)
2Mg(s) + O2(g) → MgO(s)
3 2
2
→ BaSO4(s)Al2(SO4)3(aq) + BaCl2(aq)
+ AlCl3(aq)
Challenge: **Writing Balanced Chemical Equations
Example 2. Solutions of aluminum sulfate
and barium chloride react to produce solid
barium sulfate and aqueous aluminum
chloride.
aluminum sulfate = Al3+, SO42- = Al2(SO4)3
barium chloride = Ba2+, Cl- = BaCl2
barium sulfate = Ba2+, SO42- = BaSO4
aluminum chloride = Al3+, Cl- = AlCl3
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2
33
Write a balanced equation for each of the
following reactions.
**Aluminum metal reacts with oxygen gas to
produce solid aluminum oxide.
**Solutions of calcium chloride and sodium
sulfate react to produce aqueous sodium
chloride and solid calcium sulfate.
Al(s) + O2(g) → Al2O3(s)
You Try It
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CaCl2(aq) + Na2SO4(aq)→ NaCl(aq) + CaSO4(s)
2
2
4 3
Homework/DO NOW:
14 practice problems TO BE TURNED IN when completed
[[you need a computer]]
www.socrative.com
Room code: KILBANESTP
Enter your name
1. Synthesis
A + B AB
2. Decomposition
AB A + B
3. Single Replacement
A + BC B + AC
4. Double Replacement
AB + CD CB + AD
5. Combustion Reaction
CxHy + O2 CO2 + H2O
Types of Reactions
Synthesis (Combination) Reactions
two substances – either elements or
compounds – combine to form a single
compound.
The general equation for a synthesis reaction is:
A + B → C
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Practice: Synthesis ReactionsWrite the product and balance the equation.
Remember, if you have a metal + nonmetal, you have to balance the charges!!!
1) H2 + O2
2) Zn + S
3) H2 + Cl2
4) K(s) + Cl2 (g)
5) N2 + H2
H2O
ZnS
HCl
NH3
KCl
2 2
2
2
3 2
2
Balanced
“ammonia”
Zn2+ S2- Zn2+ S2-
H+ Cl- H+ Cl-
K+ Cl- K+ Cl-
II. Decomposition Reaction: A compound breaks down into simpler products.
AB A + B
HgO Hg + O22 2
Diatomic
Metal Carbonates: break down into the
metal oxide and carbon dioxide.
CaCO3
Na2CO3
PbCO3
CaO + CO2
Na2O + CO2
PbO + CO2
Ca2+ O2-
Na+ O2-
Pb2+ O2-
III. Single Replacement ReactionOne element replaces another element.
Remember: The positive ion always goes with the negative ion!
A + BC B + AC
A) Metal replaces Metal
Cu + AgNO3
B) Nonmetal replaces Nonmetal
Br2 + KI
Cu(NO3)2 + Ag
KBr + I2
Cu2+ Ag+ NO31- Cu2+ NO3
1- Ag +
Pos. ion goes with neg. ion!
Br1- K+ I1- K+ Br1- I1-
Diatomic
Solutions of ionic compounds trade ions
Outside two go together; Inside two go
together. (+ion with ion)
AB + CD CB + AD
Double Replacement
Double-Replacement Reactions
KBr + NaCl → KCl + NaBr
MgCl2 + 2LiF → MgF2 + 2LiCl
HCl + NaOH → NaCl + H2O
(This is an example of a special type of double-replacement
reaction known as an acid-base neutralization reaction.)
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Combustion Reactions A burning of a hydrocarbon compound in oxygen
produces carbon dioxide and water.
CxHy + O2 (g) CO2 + H2O
Complete Combustion Reactions
CH4 + 2O2 → CO2 + 2H2O
2C3H7OH + 9O2 → 6CO2 + 8H2O
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Welcome to FRIDAY!Make sure you picked up the handout by the door.
Practice Sheet: your options…Single replacement
Double replacement
Synthesis
Decomposition
Acid-base neutralization
Combustion
YOU HAVE 10 MINUTES. MAY THE ODDS BE EVER IN YOUR FAVOR
35 minutes of PUTTING IT TOGETHER:Complete and balance the following equations. Label
the type of reaction.
1. HgO
2. C5H10 + O2
3. AgNO3 + NaCl
4. Li + N2
5. K + Ba(C2H3O2)2
6. H2O
7. Mg(NO3)2 + KOH
8. C6H14 + O2
9. Al + S
10. F2 + AlCl3
Decomposition2 Hg + O22
CombustionCO2 + H2O2 10 1015
Double-ReplacementAgCl + NaNO3
SynthesisLi3N26
Single-ReplacementKC2H3O2 + Ba2 2
DecompositionH2 + O22 2
Double-ReplacementMg(OH)2 + KNO322
CombustionCO2 + H2O2 12 1419
SynthesisAl2S32 3
Single-ReplacementAlF3 + Cl23 22 3Back to main menu
Activity Series
Not all single-replacement reactions will occur.
Mg + ZnCl2
Zn + MgCl2
How can you determine if a single-replacement
reaction will occur or not?
MgCl2 + Zn
No Reaction
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Whether or not a single-
replacement reaction will
occur can be determined
by using an activity series.
The activity series of
metals lists metals in order
of chemical reactivity.
A reactive metal will
replace any metal found
below it in the activity
series.
Activity Series of Metals
WRITE THIS DOWN!
The halogens can also take
place in single-replacement
reactions.
The order of reactivity for the
halogens from highest to
lowest reactivity: is fluorine,
chlorine, bromine, iodine.
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Activity of
Halogens
F2
Cl2Br2
I2
Activity Series of Halogens
Activity of
Halogens
F2
Cl2Br2
I2
Incr
easi
ng
act
ivit
y
Will the first element replace
the second?
1.Mg Ag
2.BrF
3.PbCu
4.ClI
Yes
No
Yes
Yes
Single-Replacement Reactions
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Remember: In order to replace an
element, the first element (reactant)
has to be HIGHER on the activity
series then the second
Use the activity series to determine whether or not the following
reactions will occur. If the reaction will occur spontaneously,
complete and balance the reaction. If it does not occur, write “no
reaction”.
1. Zn + Na2O →
2. Li + AgNO3 →
3. Fe + CuSO4 →
4. Cl2 + KBr
Ag + LiNO3
Cu + FeSO4
No Reaction
Single-Replacement Reactions
KCl + Br22 2
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The equation says “no reaction”, plus the picture shows that nothing
is happening. That must mean WHAT?
The metal ion originally in the solution is MORE reactive (higher on
the activity series list) then the metal that was dropped into the
solution. You could also say that the metal dropped into the
solution was lower on the list than the original metal.
In order to replace hydrogen, the
unknown element must be ABOVE the
known element. Nickel is the only
metal listed that is above Hydrogen on
the list (gold is below)
I need you to FOCUS today!
We have a LOT to do!!!
Please make sure you have the pink half sheet
Oxidation-Reduction Reactions (Redox)
Oxidation-Reduction reactions
occur when electrons are
transferred between reactions.
Examples include: the burning of
gasoline and the rusting of a nail.
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OxidationOxidation originally meant the combination of an
element with oxygen to give oxides.
However, today it is defined as:
the loss of electrons.
(Oxygen does not have to be present for oxidation
to occur.)
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ReductionReduction originally meant the loss of oxygen from
a compound.
Today it is defined as:
the gain of electrons.
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Helpful Mnemonics
Leo the Lion says Ger
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L – Loss
e – of electrons
o – is oxidation
G – Gain
e – of electrons
r – is reduction
Helpful Mnemonics
OIL RIG
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O – Oxidation
I – Is
L – LOSS
R – Reduction
I – Is
G – Gain
TIPS for Assigning Oxidation Numbers
1. The oxidation number of a
monatomic ion (by itself) is
equal to its given charge.
Examples:
Br- equals
Fe3+ equals
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-1
+3
Rules for Assigning Oxidation Numbers
2. For a polyatomic ion, the sum
of the oxidation numbers must
equal the ionic charge of the
ion.
Examples:
SO42- equals
NO3- equals
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-2
-1
Rules for Assigning Oxidation Numbers
3. The oxidation number of a
metal cation is the same as its
ionic charge.
Examples:
sodium ion is
calcium ion is
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+1
+2
Rules for Assigning Oxidation Numbers
4. The oxidation number of
hydrogen in a compound is
usually +1.
Exception: In metal hydrides,
(ex. NaH) hydrogen is -1.
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Rules for Assigning Oxidation Numbers
5. The oxidation number of
oxygen in a compound is
usually -2
Exception: In peroxides (ex.
H2O2) oxygen is -1.
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Rules for Assigning Oxidation Numbers
6. The oxidation number of an
uncombined element is 0.
For example, the oxidation number of
the potassium atoms in potassium
metal, K, and of the nitrogen atoms in
nitrogen gas, N2, is zero.
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Rules for Assigning Oxidation Numbers
7. For any neutral compound, the
sum of the oxidation numbers
of the atoms in the compound
must equal 0.
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When assigning oxidation numbers to the
elements in neutral compound or ion (positive +
negative), assign them in the following order:
1.Lone elements (not in a compound): 0
2.metal –
3.hydrogen –
4.oxygen –
5.everything that is left over
use the charge from the periodic table
+1 (or -1 in metal hydrides)
-2 (or -1 in peroxides)
Rules for Assigning Oxidation Numbers
1. What is the oxidation number of each element in the following?
SO2
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+4 -2
-4+4 =0
S = +4
O= -2
2. What is the oxidation number of each element in the following?
KClO3
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+1 -2
-6+1 =0
K = +1
O= -2
Cl = +5+5
+5
3. What is the oxidation number of each element in the following?
KClO2
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+1 -2
-4+1 =0
K = +1
O= -2
Cl = +3+3
+3
4. What is the oxidation number of each element in the following?
CO32-
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+4 -2
-6+4 = -2
C = +4
O= -2
You Try It. Determine the oxidation number of each element in each of the following on your own.
5. Na2Cr2O7 Na = Cr = O=
6. BaH2 Ba = H =
(Hint: BaH2 is a metal hydride.)
7. Li2O2 Li = O =
(Hint: Li2O2 is a peroxide.)
8. ClO3- Cl = O =
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+2
+6 -2+1
-1
+1 -1
+5 -2
Oxidation Number Changes
The changes in oxidation number can be
used to determine which elements are
oxidized and which elements are reduced.
Remember – an increase in the oxidation
number of an atom signifies oxidation and a
decrease in the oxidation number signifies
reduction.
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Oxidation Number ChangesUse the change in oxidation number to
identify which elements are oxidized and
reduced in each of these reactions.
1. F2(g) + 2HBr(aq) → 2HF(aq) + Br2(l)
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0 +1 -1 +1 -1 0
Fluorine: 0 to -1; reduced
Bromine: -1 to 0; oxidized
=0+1 -1 =0+1 -1
Oxidation Number ChangesUse the change in oxidation number to
identify which elements are oxidized and
reduced in each of these reactions. Also
identify the oxidizing (OA) and reducing (RA)
agents.
3. SO3(g) + H2O(l) → H2SO4(aq)
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+6 -2 +1 -2 +1
Since there is no change in oxidation
number, this is not a redox reaction.
-6+6 +2
-2
-8+6
+6
+2 -2=0 =0 =0
Oxidation Number ChangesUse the change in oxidation number to
identify which elements are oxidized and
reduced in each of these reactions. Also
identify the oxidizing (OA) and reducing (RA)
agents.
2. 2KClO3(s) → 2KCl(s) + 3O2(g)
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+1 -2+5 +1 -1 0
Chlorine: +5 to -1; reduced
Oxygen: -2 to 0; oxidized
-6+1 +5 =0 =0+1 -1
You Try ItUse the change in oxidation number to
identify which elements are oxidized and
reduced in each of these reactions. Also
identify the oxidizing (OA) and reducing (RA)
agents.
4. 2H2(g) + O2(g) → 2H2O(g)
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0 0 +1 -2
+2
hydrogen: 0 to +1; oxidized
oxygen: 0 to -2; reduced
-2 =0
You Try ItUse the change in oxidation number to
identify which elements are oxidized and
reduced in each of these reactions. Also
identify the oxidizing (OA) and reducing (RA)
agents.
5. 2Al(s) + 6HCl(aq) → 2AlCl3(s) + 3H2(g)
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0 0+1 +3
+3
aluminum: 0 to +3; oxidized
hydrogen: +1 to 0; reduced
-3
-1 -1
=0+1 -1 =0
You Try It
You Try It… DO MORE
OH SNAP! Last day before the EXAM! Today’s agenda:
1. Double Replacement and Solubility Rules (you need a purple chart if you don’t have one yet)
2. Solubility Practice
3. Test Review
Announcements:
Our exam is onWEDNESDAY Feb. 17th
Please check your home access to determine what you’re missing.
The 6 weeks ends onFriday Feb. 19th
82
Soluble and Insoluble SaltsIonic compounds that
dissolve in water are soluble salts
do not dissolve in water are insoluble salts
83
Solubility Rules Soluble salts typically contain at least one ion
from Groups 1A(1), NO3−, or C2H3O2
− (acetate).
Most other combinations are insoluble.
You have this
chart (or you
should). Yours is
purple!!
How do you use this
crazy looking thing?>!
1. Look at the second
element/ion in the given
compound.
NaOH
2. Find in under “soluble or
insoluble”
NaOH
OH is insoluble, unless it’s paired
with an exception.
3. Check to see if it is paired with
an exception. If it IS with an
exception, it becomes the
opposite (soluble becomes
insoluble)
NaOH
Na is an alkali metal, which means
that it’s an exception. This means
that NaOH is SOLUBLE!!
85
Use the solubility rules to determine if each
salt is:(S) soluble or (I) insoluble.
A. Na2SO4
B. MgCO3
C. PbCl2
D. MgCl2
Learning Check
Soluble
Insoluble
Insoluble
Soluble
For the rest of the period:
you are to work on your
study guide.
This will be EXTRA CREDIT
if you complete it and
turn it in on test day.