Transcript Types of Chemical Reactions

Unit 8- Chemical Reactions
Mass and Change Lab
• Goal- What happens to the mass of an object
when they are changed?
Part 1:
Part 2:
Part 3:
Part 4:
Part 5:
Change the shape of steel wool
Melting ice
Burning steel wool
Dissolved sugar in water
Dissolved Alka-Seltzer
Data
Change the shape of steel wool
PredictionMass Before
Mass After
Change
The lab groups should report their results on the board so that
the entire class data can be recorded. Change should be
recorded as + (for a gain) or – (for a loss).
Group
Change in mass (g)
Law of Conservation of Mass
• This law was developed by a
French chemist named Antoine
Lavoisier.
• Lavoisier carefully measured
the mass of the reactants and
products when carrying out
chemistry experiments.
• He noticed that in every case,
the mass of the reactants was
ALWAYS equal to the mass of
the products.
•Law of Conservation of Mass
• Historical Context- Year was 1776.
– He was the first scientist to recognize and name
the elements hydrogen and oxygen.
– In 1789, he wrote the first
chemistry textbook.
• Oxygen, nitrogen, hydrogen,
phosphorus, mercury, zinc and sulphur (list also included
'light' and 'caloric‘).
– He was executed, along with hundreds of other
nobles, during the French Revolution.
Law of 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.
• The mass of the reactants equals the
mass of the products.
massreactants = massproducts
Plan of Attack
1. Take pre-assessment on back.
2. Follow the directions step by step.
- app i-nigma to read the qr-code
3. I will be walking around to verbally asses
understanding and stamping.
4. If you get done and I have not stamped you,
please raise your hand and quietly wait.
N2 (g) + H2 (g) -------> NH3 (g)
End of Day
Chemical Reactions
• Key Concept 2: 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
• Chemists use statements called equations
to represent 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
(cont.)
• In word equations, aluminum(s) +
bromine(l) → aluminum bromide(s) reads
as “aluminum and bromine react to
produce aluminum bromide”.
• Key Concept 3: Skeleton equations use
symbols and formulas to represent the
reactants and products.
Al(s) + Br(l) → AlBr3(s)
Skeleton equations lack information about
how many atoms are involved in the reaction.
Representing Chemical Reactions
(cont.)
• 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 Equations
• This figure shows the balanced equation
for the reaction between aluminum and
bromine.
Balancing Chemical Equations
(cont.)
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)
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 Equations
(cont.)
Balancing Chemical Equations
(cont.)
Balancing Chemical Equations
(cont.)
Balancing Chemical Equations
(cont.)
• Key Concept 5: The most fundamental law
in chemistry is the law of conservation of
mass.
• Balanced equations show this law.
Balancing Chemical Equations
• Key Concept 6: Steps
(cont.)
Balancing Chemical Equations
(cont.)
Two helpful hints
1) Never start with balancing oxygen; you
can get into a crazy never ending loop.
(But, if oxygen is odd, try to make them not
odd at the start).
2) If a polyatomic ion exists on both sides of
the equation you can keep it together if
balancing is giving you trouble.
Balancing Chemical Equations
Key Concept 7: H2 + O2 → H2O
C2H2 + O2 → H2O + CO2
(cont.)
Balancing Chemical Equations
(cont.)
Key Concept 8: Dinitrogen pentoxide gas in
the presence of a platinum catalyst and high
enough temperature forms nitrogen gas and
oxygen gas.
Balancing Chemical Equations
(cont.)
Voltage is applied to two electrodes in a solution of
iron (III) chloride and a yellow-green gas bubbles
form on one electrode and metallic deposits form on
the other electrode.
Assessment
What is the coefficient of bromine in the
equation 2Al(s) + 3Br2(l) → 2AlBr3(s)?
A. 1
B. 2
C. 3
D. 6
A.
B.
C.
D.
A
B
C
D
Jeopardy Closure
1. Answer: These are added to chemical reactions
to not break the Law of Conservation of Matter
2. Answer: When balancing a chemical reaction
these cannot be changed
3. Answer: These are changed into a new
substances after a reaction.
End of Day
Types of Chemical Reactions
synthesis reaction
combustion reaction
decomposition reaction
single-replacement reaction
double-replacement reaction
precipitate
Classifying Chemical Reactions
Key Concept 9: There are four
types of chemical reactions:
synthesis, combustion,
decomposition, and replacement
reactions.
Types of Chemical Reactions
Types of Chemical Reactions
Type of Reaction:
Key Concept 10: Synthesis reaction
Explanation: Reaction in which two or
more simpler substances (elements)
react to produce a single product
(compound).
Types of Chemical Reactions (cont.)
• Other: When two elements react, the
reaction is always a synthesis reaction.
General Equation:
A +
B
AB
Types of Chemical Reactions
Type of Reaction:
Key Concept 11: Decomposition
Reaction
Explanation: Reaction in which a
single compound breaks down into
two or more elements or new
compounds.
Decomposition Reactions
• Other: Decomposition reactions often require
an energy source, such as heat, light, or
electricity, to occur.
General Equation:
AB
A
+
B
Types of Chemical Reactions
Type of Reaction:
Key Concept 12: Combustion
Reaction
Explanation: Reaction where
oxygen combines with a substance
(normally contains carbon) and
releases energy in the form of heat
and light.
Types of Chemical Reactions (cont.)
General Equation:
___
+
O2
H2O + CO2
CH4 (g) + O2 (g)  CO2 (g) + H2O (g)
Hunting the Elements (Start at 9:40 to 20:12)
Types of Chemical Reactions
Correctly Identify the type of reaction:
S = synthesis
D = decomposition
1.
NH3+ H2SO4  (NH4)2SO4
2.
C5H9O + O2  CO2 + H2O
3.
H2 + O2  H2O
4.
NH4OH  NH3 + H2O
5.
KClO3 (s)  KCl (s) + O2 (g)
6.
Al (s) + S (s)  Al2S3 (s)
7.
NaNO3 (s)  NaNO2 (s) + O2 (g)
8.
CO (g) + O2 (g)  CO2 (g)
9.
CH4 (g) + O2 (g)  CO2 (g) + H2O (g)
10. Mg + N2  Mg3N2
C = combustion
Types of Chemical Reactions
Type of Reaction:
Key Concept 13: Single Replacement
Explanation: Reaction in which the
atoms of one element replace the
atoms of another element in a
compound.
Replacement Reactions
General Equation:
Metals
A + BX
Halogen Y2 + BX
AX + B
BY + X2
• Other Info: A metal will not
always replace a metal in a
compound dissolved in
water because of differing
reactivates.
• An activity series can be
used to predict if reactions
will occur.
Hydrogen gas
goes here
Types of Chemical Reactions
• Write a balanced chemical equation for each
single-replacement reactions involving metals.
• Zn (s) + AgNO3 (aq)
• Zn(s) + H2SO4 (aq)
• Na(s) + H2O(l)
Types of Chemical Reactions
• Write a balanced chemical equation for each
single-replacement reactions involving halogens
• Cl2 (g) + HBr(aq)
• I2 + HCl2 (aq)
•
Simulations
Types of Chemical Reactions
Type of Reaction:
Key Concept 14: Double Replacement
Explanation: Reaction in which the ions
exchange between two compounds.
Replacement Reactions (cont.)
General Equation:
Replacement Reactions (cont.)
• Other: All double replacement reactions
produce either water, a precipitate, or a
gas.
• The solid product produced during a
chemical reaction in a solution is called a
precipitate.
Replacement Reactions (cont.)
Types of Chemical Reactions
• Write a balanced chemical equation for
each double-replacement reactions
BaCl2(aq) + K2CO3 (aq)
FeS (s) + HCl (aq)
(a precipitate of barium
carbonate is formed)
(Hydrogen sulfide gas is
formed)
Get out your practice problems.
Exit Pass
The following equation is what type of
reaction?
1. KCN(aq) + HBr(aq) → KBr(aq) + HCN(g)
A. decomposition
B. synthesis
C. combustion
D. single replacement
E. double replacement
A.
B.
C.
D.
A
B
C
D
Exit Pass
The following equation is what type of
reaction?
2. CO (g) + O2 (g)  CO2 (g)
A. decomposition
B. synthesis
C. combustion
D. single replacement
E. double replacement
A.
B.
C.
D.
A
B
C
D
Section Assessment
The following equation is what type of
reaction?
3. NaNO3 (s)  NaNO2 (s) + O2 (g)
A. decomposition
B. synthesis
C. combustion
D. single replacement
E. double replacement
A.
B.
C.
D.
A
B
C
D
So what do I really have
to be able to do?
• Identify what type of reaction a chemical
equations is.
• Predict if a single replacement reaction will
happen and what the products would be.
• Predict the products of a double replacement
reaction.
Replacement Reactions (cont.)
• Key Concept 15:
Types of Chemical Reactions
• Write a balanced chemical equation for
each double-replacement reactions
BaCl2(aq) + K2CO3 (aq)
FeS (s) + HCl (aq)
(a precipitate of barium
carbonate is formed)
(Hydrogen sulfide gas is
formed)
Get out your practice problems.
Solution
Everyday definition
• Answer to a problem
• A type of liquid
Chemistry
• Solution- uniform
mixture that can
contain solid, liquid, or
gases
Solution = Homogenous mixture
They are synonyms
How a solution is made?
• Solution consist of a solvent
and solute.
• Key Concept 16: Solvent- the
substance that dissolves the
solute to form a solution;
most plentiful substance in
the solution.
• Key Concept 17: Solute- one
or more substance dissolved
in a solution.
• Dissociation
Solubility
• Solubility is physical properties.
– Physical properties are those properties that can
be observed or measured without affecting the
composition of the sample.
• Solubility is the maximum quantity of a
substance that may be dissolved in another.
The maximum amount of solute that may be
dissolved in a solvent.
Effect of Temperature on Solubility
Solubility
• depends on temperature
• of most solids increases as
temperature increases
• of gases decreases as temperature
increases
• What is sodium chlorides solubility?
– Water: 359 g/L
– Ammonia: 21.5 g/L
– Methanol: 14.9 g/L
Soluble and Insoluble Salts
Ionic compounds that
• dissolve in water are
soluble salts
• do not dissolve in
water are insoluble
salts
•59
Key Concept 18: Quick DR Visual
Lead (II) Nitrate
Pb(NO3) 2
1.
2.
3.
4.
Sodium Chloride
NaCl
How do I make an solution?
What is the solvent and the solute?
What happens during dissociation?
What happens in a double replacement reaction?
Pb(NO3) 2 (aq) + 2NaCl(aq)  PbCl2(s) + 2NaNO3(aq)
This Week’s plan of attack
• Today- Complete last three station (if you an
your partner get done, work on practice
problems)
• Tuesday- Start Double Replacement Lab
• Wed- (35 min classes) Complete three more
stations
• Thursday- Finish Double Replacement Lab
(due Friday)
• Friday- Acid and Bases
Determining Solubility to Solve Double
Replacement Reaction (70 pts)
Part 1:
(2.5 pts) Purpose: To determine whether or
not a reaction occurs and to predict the
products of a reaction.
Determining Solubility to Solve
Double Replacement Reaction
(7.5 pts) Safety:
• We are working with acids; gloves, goggles, and aprons must
be worn properly at all times.
• All chemicals must be disposed of in specified waste beakers
in the fume hoods. These chemicals are toxic and will harm
the environment if not disposed of properly.
• Do not eat, drink, or apply the chemicals to skin. Many of
these chemicals are highly corrosive and in addition to being
toxic, they will burn your skin and muscle tissue. Ouch!
• If any of the chemicals get on your skin/eyes you MUST wash
exposed area for 15 minutes in eye wash/shower.
Determining Solubility to Solve
Double Replacement Reaction
(10 pts) Data Table
and Results
Beginning
HCl
H2SO4
NaOH
Nitrate
added
added
added
LiNO3
KNO3
Mg(NO3)2
Ca(NO3)2
Co(NO3)2
Cu(NO3)2
AgNO3
Pb(NO3)2
Determining Solubility to Solve
Double Replacement Reaction
(10 pts) Part 21. All nitrate salts are __________.
2. Most salts containing ______ and ________ cations are
soluble.
3. All cations from ______________ are soluble. In addition
NH4+1 salts are soluble.
4. Salts with halogen anions are usually _____________.
5. Most sulfate salts are __________. Exceptions include the
cations __________ and ____________.
6. Hydroxides are usually ___________ except those containing
cations from __________.
Determining Solubility to Solve
Double Replacement Reaction
(20 pts) Part 31-11 You will need to answer the questions
by predicting products of the double
replacement reaction.
(20 pts) Part 4Using solubility tables and charts
Key Concept 19: What is an Acid?
•pH less than 7
•Neutralizes bases
•Acids increase H+ cation
concentration in water.
What is an Acid?
Key Concept 20:
Common Acid
• HCl- hydrochloric- stomach acid
• H2SO4- sulfuric acid - car batteries
• HNO3 – nitric acid - explosives
• HC2H3O2- acetic acid - vinegar
• H2CO3-carbonic acid – sodas
• H3PO4- phosphoric acid -flavorings
Key Concept 21: What is an Base?
• pH greater than 7
• Neutralizes acids
• Forms OH ions in solution
Common Bases
•
•
•
•
NaOH- sodium hydroxide (LYE) soaps, drain cleaner
Mg (OH)2 - magnesium hydroxide-antacids
Al(OH)3-aluminum hydroxide-antacids, deodorants
NH4OH-ammonium hydroxide- “ammonia”
What is an Base?
Key Concept 22 :
Acids and Bases
• Common acids include HCl, HNO3, and H2SO4
• Common bases include NaOH, LiOH, and KOH
• Key Concept 23: Predict the products of these
acid-base rxns:
HCl + NaOH 
HNO3 + LiOH 
H2SO4 + KOH 
Do we notice any patterns?
Acid and Bases
All double replacement reactions produce
either water, a precipitate, or a gas.
Acids and Bases
• Because the reaction is a type of doublereplacement reaction, H+ and OH- always form
a product of H2O and the other ionic
compound is always a salt.
• Key Concept 24:The products of a reaction
between acids and bases are always a salt and
water.
Acids and Bases
• The question becomes how much of the
solution is water, and how much is acid/base?
• If the ratio of acid/base to the amount of
water is high, then the solution is considered
to be strongly acidic or strongly basic.
• Key Concept 25 : The strength of a solution
can be quantified in two ways: pH and
Molarity.
Acids and Bases
• pH is typically on a scale of 1-14, however
there can be pH values outside of that range.
• Key Concept 26: A pH of 7 is considered to be
completely neutral, non-acidic and non-basic.
– Any solution with pH < 7 is considered acidic.
– Any solution with pH > 7 is considered basic.
Digestion and pH
• Digestion-process by which foods are broken down
into simpler substances.
• Mechanical digestion-physical process in which food is
torn apart (mouth)
• Chemical digestion- chemical reactions in which large
molecules are broken down into smaller molecules.
(stomach and small intestines)
Digestion and pH
• Mouth-pH around 7. Saliva contains
amylase, an enzyme which begins to break
carbohydrates into sugars.
• Stomach- pH around 2. Proteins are broken
down into amino acids by the enzyme
pepsin.
• Small intestine-pH around 8. Most digestion
ends. Small molecules move to bloodstream
toward cells that use them
Acids and Bases
• In biology and chemistry we can use indicators
to approximate a solution’s pH.
• Key Concept 27: Indicators are chemicals that
show different colors above and below the
indicator’s pH constant.
• The color and the pH range it changes colors
at vary for different indicators.
• The most common indicator, phenolphthalein,
turns pink in basic solutions (pH > 7) and clear
in acidic solutions (pH < 7).
Acids and Bases
Natural Acids and Bases Indicators
Acids and Bases
• An acid’s or base’s strength can also be
measured in terms of “Molarity”.
• Key Concept 28:Molarity is a measure of the
concentration in terms of moles of acid/base
per liter of water.
• Molarity can be expressed with a capital “M”
or as a conversion factor: X mol = 1 liter
• Molarity has a wider range of application than
pH, especially in chemistry.
• Molarity is also required to calculate pH.
Acids and Bases
• Three chemicals were made
with the following procedures:
– 3.0 mol HCl in 1 liter of water.
3.0 mol HCl
1 liter
– 5.5 mol NaOH in 1 liter of water. 5.5 mol NaOH
1 liter
– 4.0 mol HNO3 in 2 liters of water. 4.0 mol HNO3
2 liters
= 3.0 M HCl
= 5.5 M
NaOH
= 2.0 M
HNO3
Which is the strongest Acid? (5)
3.0 M HCl is the strongest
Acid
Acids and Bases
• Three chemicals were made
with the following procedures:
– 2.7 mol H2SO4 in 2 liters of water. 2.7 mol HCl
2 liter
= 1.35 M
H2SO4
– 1 mol NaOH in 0.5 liters of water. 1 mol NaOH
= 2.0 M
NaOH
– 6.6 mol LiOH in 6 liters of water. 6.6 mol HNO3
= 1.1 M LiOH
0.5 liter
6 liters
Which is the strongest base?
2.0 M NaOH is the strongest
Base
Practice
What ions are responsible for a acidic solution?
Practice
What ions are responsible for a basic solution?
Practice
What is the general conversion factor for
Molarity?
Practice
How does an indicator help us estimate pH?
Practice
What are the products when an acid react with
a base?