Transcript Chemistry: Matter and Change

BRN
5H2
1. What number represents the coefficient?
2. What number represents the subscript?
3. What element is represented by the letter “H”?
4. How many “H’s” do you have?
BRN
KNO3 (s)
→ KNO2 (aq) + O2 (g)
1. What compound(s) are the reactants?
2. What compound(s) are the products?
3. What compound is found in the gas state?
Chemical Reactions
Notes
New section in table of contents
Conservation of Mass
 Key Concept 1: The law of conservation of
mass states that mass is neither created nor
destroyed in a chemical reaction, it is
conserved.
 KC 2: The mass of the reactants equals the
mass of the products.
massreactants = massproducts
Chemical Reactions
 KC 3: The process by which one or more
substances are rearranged to form different
substances is called a chemical reaction
 What are some examples of evidence of a
chemical reaction?
Representing Chemical
Reactions
 Reactants are the
starting substances.
 Products are the
substances formed in
the reaction.
 This table summarizes
the symbols used in
chemical equations.
Representing Chemical
Reactions
 Key Concept 4: A chemical equation is a
statement that uses chemical formulas to show
the identities and relative amounts of the
substances involved in a chemical reaction.
Balancing Chemical Reactions
 KC 5: Subscripts describe the number of atoms
present in one molecule (if it is a molecular
compound) or in one formula unit (if it is an ionic
compound).
N2 (g) +
H2 (g) ------->
NH3 (g)
 KC 6: Coefficients are generally used for balancing
the chemical equations in accordance with the
law of conservation of mass.
N2 (g) + 3 H2 (g) -------> 2 NH3 (g)
Balancing Chemical Reactions
 Balancing reactions is like a puzzle, you need
to make sure both sides of the equation are
equal
 Helpful Hints:
 Start with either polyatomic ions or carbon
containing molecules
 Never start with balancing oxygen
 Write water as HOH (can be easier to see if OH is
present on both sides)
Balancing Chemical Reactions
 KC 7:
H2 + O2 → H2O
Balancing Chemical Reactions
 KC 8:
Fe + H2O → H2 + Fe2O3
Balancing Chemical Reactions
 KC 9: Dinitrogen pentoxide gas forms nitrogen
gas and oxygen gas.
Types of Chemical Reactions
KC 10: There are 4 types of chemical
reactions
Synthesis
Combustion
Decomposition
replacement
Don’t forget…
 Some molecules are more stable when they are found
as diatomic – two of the same element covalently
bonded
B I N C H O F
r o i h y x l
o d t l d y u
BrINClHOF m i r o r g o
i n o r o e r
n e g i g n i
e
e n e
n
n e n
e
Bonding
Evidence of a Chemical
Reaction
 KC 11: There are 3 driving forces that are
evidence of a chemical reaction:
 Evolution of a gas
 Production of heat
 Production of a solid or pure liquid (water)
Types of Chemical Reactions
 KC 12: Synthesis – reaction in which 2 or more
simpler substances (elements) react to
produce a single product (compound)
 General Reaction : A + B → AB
 synthesis
Types of Chemical Reactions
KC 13: Combustion – reaction where
oxygen combines with a substance
(normally contains carbon) and releases
energy in the form of heat and light
General Reaction:
demo
CxHy + O2 → H2O + CO2
Types of Chemical Reactions
KC 14: Decomposition – Reaction in
which a single compound breaks down
into 2 or more elements or new
compounds
General Reaction: AB → A + B
demo - 3:00
Types of Chemical Reactions
KC 15: Correctly identify and balanceeach type of rxn
S = synthesis
D = decomposition
C = combustion
1. _______
___NH3+ ___H2SO4  ___(NH4)2SO4
2. _______
__C5H9O + ___O2  ___CO2 + _H2O
3. _______
___H2 + ___O2  ___H2O
4. _______
___NH4OH  ___NH3 + ___H2O
5. _______
___CO + ___O2  ___CO2
Closure – Exit Pass
1. This type of reaction always forms products of carbon
dioxide and water
a. Synthesis
b. Decomposition
c. Combustion
2. What type of reaction has the general format AB → A + B
a. Synthesis
b. Decomposition
c. Combustion
Types of Chemical Reactions
 KC 16: Single Replacement – Reaction in
which the atoms of one element replace the
atoms of another element in a compound
 General Reaction:
A + BX → AX + B
 Other Information: A metal will not always replace a
metal in a compound dissolved in water because of
differing reactivities
Single Replacement Reactions
 Elements will not always
replace each other in a
single replacement
reaction
 The activity series tells us if
the replacement will
occur
 Elements replace lower
elements in the chart, but
not the other way around
Single Replacement
 Zn(II) (s) + AgNO3 (aq) →
 Cl2 (g) + HBr(aq) →
 Na(s) + CaO(aq) →
Fe(III) + PbSO4 →
1. See if the reaction will
occur using reactivity
series
2. Identify the charges of the
elements
3. Do single replacement to
predict the products
(*same charges switch))
4. Balance the reaction using
coefficients
Single Replacement Practice
 I2 + HCl2 →
 Zn(II) + Cu2SO4
 AlCl3 + Mg →
 Cu(I) + Ag2SO4 →
 LiNO3 + Ag →
 Fe(II) + PbSO4 →
→
Types of Chemical Reactions
 KC 17: Double Replacement – reaction in which
the ions exchange between 2 compounds. All
double replacement reactions produce either
water, a precipitate, or a gas
 General Reaction: AX + BY → AY + BX
Types of Chemical Reactions
 KC 18: The solid produced during a chemical
reaction is called a precipitate.
 Precipitation comes from the clouds –
“precipitates out”
Writing Reactions
KC 19: Write a balanced chemical equation for
each double-replacement reactions
BaCl2(aq) + K2CO3 (aq)
(a precipitate of barium
carbonate is formed)
FeS (s) + HCl (aq)
(Hydrogen sulfide gas is
formed)
BaCl2(aq) + K2CO3 (aq)
FeS (s) + HCl (aq)
Predicting Reactions Practice
1. Barium chloride + sodium sulfate → precipitate
of barium sulfate is formed
Predicting Practice
 Silver (I) nitrate + calcium sulfide → precipitate
of silver sulfide is formed
Practice
 Potassium carbonate + hydrochloric acid (HCl)
→ a precipitate of hydrogen carbonate is
formed
Practice
 Sodium sulfate + barium nitrate → a precipitate
of barium sulfate is formed
Solubility
 KC 20: Solubility is the maximum quantity of a
substance that may be dissolved in another
 Solubility…
 Depends on temperature
 Of most solids increases as temperature increases
 Of gases decreases as temperature increases
White
Solid
Water +
Water (at
room
universal
indicator temperature)
HCl
Baking
Soda
Green
Slightly
soluble
Sugar
Yelloworange
Soluble
----------
Benzoic
Acid
Pink
Insoluble
----------
Flour
Orange
Insoluble
----------
Sodium
Chloride
Orange
soluble
----------
Methanol Iodine
Produces
--------Insoluble
gas
Turns
blue
--------Soluble
Turns
Insoluble
blue
Insoluble
Slightly
soluble
---------
Temp of
solubility in
water
50 C
20 C
100 C
insoluble
20 C
Soluble and Insoluble Salts
KC 21: Ionic compounds
that
 dissolve in water are
soluble salts
 do not dissolve in
water are insoluble
salts
Using Solubility Rules
 Ba(NO3)2(aq) + Li2SO4(aq) →
 What does this actually look like?
Equations for Forming Solids
A full equation shows the formulas of the
compounds.
Pb(NO3) 2(aq) + 2NaCl(aq)
2NaNO3(aq)
PbCl2(s) +
An ionic equation shows the ions of the
compounds.
Pb2+(aq) + 2NO3−(aq) + 2Na+(aq) + 2Cl−(aq)
PbCl2(s) + 2Na+(aq) + 2NO3−(aq)
Equations for Forming Solids
Pb2+(aq) + 2NO3−(aq) + 2Na+(aq) + 2Cl−(aq) → PbCl2(s) + 2Na+(aq) + 2NO3−(aq)
 Key Concept 22: A net ionic equation shows only the
ions that form a solid or water or gas.
Pb2+(aq) + 2Cl−(aq)
→
PbCl2(s)
 The ions that do not form the solid are called spectator
ions
2NO3−(aq) + 2Na+(aq) → 2Na+(aq) + 2NO3−(aq)
Predicting Reactions
 KC 23: Write the full and net ionic equation for
the following reaction – calcium carbonate +
potassium phosphate
Predicting Reactions
 KC 24: Write the full and net ionic equation for
the reaction when calcium chloride reacts with
cobalt (II) sulfate
Predicting Reactions
 KC 25: Write the full and net ionic equation
when lithium sulfide reacts with calcium nitrate
Summary
 video
Closure – Exit Pass
1. What is not always an indication that a chemical reaction
has occurred?
a. Evolution of a gas
b. Production of water
c. Color change
d. Production of heat
2. What is the reaction type that follows this general pattern –
AX + BY → AY + BX
a. Single replacement
b. Double replacement