chapter 7 chemical reactions 7-1 describing reactions in a chemical __________, the substances that...
TRANSCRIPT
Chapter 7Chapter 7Chapter 7Chapter 7
Chemical ReactionsChemical Reactions
7-1 Describing Reactions
• In a chemical __________, the substances that undergo change are called ___________
• The new substances formed as a result of that change are called ___________
• _________ ____________• Ex. Carbon + oxygen carbon dioxide• ________ equation
Chemical equations• Ex. C + O2 CO2
• Chemical _________• A chemical __________ is a
representation of a chemical reaction in which the reactants and products are expressed as ____________
Conservation of Mass• During chemical reactions, the________
of the products is always_______ to the mass of the reactants.
• Established by Antoine Lavoisier and is known as the_____________________
• The law of conservation of mass states that mass is neither _________ nor __________ in a chemical reaction
How is mass conserved in chemical change?
Activity• Follow the directions on page 191 in
your book• Fill out following information• Mass of the bag and the water=____________• Mass of a square piece of paper with sides
10cm__________________• Mass of the tablet and the paper together____________• Mass of just the tablet_______________• The combined masses of the bag, the water, and the
tablet___________• Mass of the bag and its contents_____________
Activity questions1. How do you know whether a
chemical change took place?
Activity Question• What happened to the mass of the
plastic bag and its contents after the bubbling stopped?
• What might this information tell you about a chemical change?
Balancing Equations7-1 Continued
• In order to show that mass is conserved during a reaction, a chemical equation must be _________
• You can balance a chemical equation by changing the_________, the numbers that appear _________ the formulas
• As you balance equations, you should never change the ___________ in a formula
Steps to balancing equations
1. Count the _________ of atoms of each element on each side of the equation
2. Ex: N2H4 + O2 N2 + H2O3. Left side has ____ nitrogen,____hydrogen,
and ______ oxygen atoms4. The right side has
____nitrogen,_____hydrogen, and____oxygen atom
5. The hydrogen and oxygen atoms need to be_______.
Steps to balancing equations
6. Change one or more coefficients until the equation is balanced
_1_N2H4 + _1_O2 _1_N2 + _2_H2O
• The equation is now balanced• Each side has _____ nitrogen,_____
oxygen, and _______ hydrogen atoms
Practice Balancing equations problems
1. ___Na + ___H2O ____NaOH + ___H2
2. ___HCl + ___CaCO3 ____CaCl2 +___CO2 + ____H2O
3. ____Al + ____Cl2 _____AlCl3
4. ___Cu + _____O2 _____CuO
5. ____H2O2 ____H2O + ____O2
What is a MOLE?It is a number of things….. - Just like a dozen
1 dozen eggs = 12 eggs
So, instead of 12 the mole is equal to 602 billion trillion
– OR-
6.02 x 1023
602 000 000 000 000 000 000 000
Just How Big is a Mole?6.02 X1023
Pennies:
Would make at least 7 stacks that would reach the moon.
How Big is a mole?Cover the earth to a depth of 200 miles
with soft drink cans.
Cover the USA to a depth of 9
miles of unpopped popcorn kernels.
The mole is many things….
1 dozen cookies = 12 cookies1 mole of cookies = 6.02 x 1023 cookies
1 dozen cars = 12 cars 1 mole of cars = 6.02 x 1023
cars
1 dozen Al atoms = 12 Al atoms1 mole of Al atoms = 6.02 x 1023 atoms
NOTE: the mole is abbreviated mol (gee, that’s a lot quicker to write……)
Molar Mass• Mass of 1 ______ of a pure
substance• Numerically equal to the atomic
mass but expressed in _______• The atomic mass of carbon is
12.0____, so the molar mass of carbon is 12.0_____
•What is the molar mass of the following:
• Potassium ?
Nickel ?
•What is the atomic mass of the following:
• Potassium ?
Nickel ?
Practice • What is the molar mass of the
following:1. KCl2. C2H6
3. CaCO3
4. H2O
Homework/More Practice
• What is the molar mass of the following:
1. HCl2. NaCl3. CaO
Homework/More Practice
• Balance the following___Na + ____H2O ___H2 + ___NaOH
___C2H6 + ____O2 ___CO2 + ___H2O
Beaker Breaker• Calculate the molar mass of the
following:
• MgCl2
• CaBr2
Gram- Mole Conversions
How many grams are needed to have 0.852 moles gold?
• 0.852 mol Au g Au 1 mol Au
= ______g Au
Convert 2.50moles of KClO3 to grams
Calculate how many grams are in 0.700moles of H2O2?
How many moles are in 55 g of lead?
• g Pb mol Pb 1 g Pb
• = _______moles Pb
How many moles are in 86.1 g sodium?
• 86.1 g ? mole Na = 1 ? g
• 86.1 g mole Na = 1 g• _______moles Na
How many moles are in 22 grams of copper metal?
7-2 Types of Reactions• General types of chemical reactions1. ______________2. ______________3. ______________4. ______________5. ______________
Single Replacement• ________________ reaction is a
reaction in which one element takes place of another element in a compound.
• A + BC B + AC
Teacher Demonstration• See handout
• Cu + 2AgNO3 2Ag + Cu(NO3)2
• Copper replaces the silver nitrate to form copper(II) nitrate
• The products is_______, which you can see. The other product is_____________, gives the solution its blue color.
7-2 Continued Reactions as Electron Transfer
• The discovery of subatomic particles enabled scientists to classify certain chemical reactions as transfers of_______________ between atoms.
• A reaction in which electrons are transferred from one reactant to another is called an ____________________ reaction, _________ reaction
Oxidation• Synthesis reactions, in which
a____________combines with__________, traditionally have been classified as oxidations.
• 2Ca +O2 2_________• Ca Ca+2 + 2e-• Calcium ________ two electrons• A reactant is_________ if it loses
electrons
Reduction• As calcium atoms lose electrons during the
synthesis of calcium oxide, the oxygen________ electrons
• O + 2e- O2-
• The process in which an element gains electrons during a chemical reaction is called____________
• A reactant is said to be______________ if it gains electrons.
• Oxidation and reduction always occur________.
Beaker Breaker• Identify the following reactions as
either synthesis, decomposition, single replacement, double replacement, or combustion:
2C2H6 + 7O2 4CO2 + 6H2O
Ca + 2HCl CaCl2 + H2
Beaker Breaker Cont.• Write a paragraph explaining why
the formation of water can be classified as a synthesis or combustion.
7-3 Energy Changes in Reactions
Chemical Bonds and Energy• Heat produced by a_________(C3H8) grill
is a form of energy• Balance equation:• C3H8 + ____O2 ___CO2 +___H2O
• _________ will be added to the right side of the equation
Propane Combustionusing models
• C3H8 + 5O2 3CO2 + 4H2O
• Open to page 207 follow Figure 17
Chemical Energy• _____________ is the energy stored
in the chemical bonds of a substance.
• Using the models to make C3H8 (propane)• How many C-H bonds_________• How many C-C bonds_________
Chemical Bonds• Chemical _________ involve the________ of
chemical bonds in the __________ and the_______ of chemical bonds in the ________.
• Each propane molecule reacts with_______ oxygen molecules.
• In order for the reaction to occur, the ____ C-H single bonds, _____ C-C single bonds and____O=O double bonds must be broken.
• Breaking bonds require energy• Propane grills require a igniter to provide
enough energy to ________the bonds
Chemical Bonds• After the reaction of propane (it is burned)
occurs, ______molecules of carbon dioxide (CO2) and ______ molecules of water (H2O) are formed.
• There is _____ C=O double bonds and ____ O-H single bonds formed as the ________.
• Forming bonds__________ energy• ________and ________ given off by a propane
stove are the results from the formation of the new chemical bonds
Homework• Section 7-2 Review• #1 , 3, 4, 5
Beaker Breaker• Identify the following reactions as either single
displacement, double displacement, decomposition, synthesis, or combustion
1. NaCl + H2SO4 K2SO4 + H2O
2. CaO + CO2 CaCO3
3. MgCl2 Mg + Cl2
7-3 ContinuedExothermic and Endothermic
Reactions• During a chemical reaction, energy is
either ________ or ___________• A chemical reaction that_________
energy to its surroundings is called an_____________ reaction
• Ex: Freezing• A chemical reaction that__________
energy from its surroundings is called an____________
• Ex: Melting
Exothermic Reactions• In exothermic reactions, the energy
released as the products form is __________ than the energy required to break the bonds in the reactants
• Example – Combustion• C3H8 + 5O2 3CO2 + 4H2O +
2220kJ
Endothermic Reactions• In an endothermic reaction, more
energy is required to___________ the bonds in the reactants than is released by the formation of the products.
• Example: The decomposition of mercury (II) oxide
• 2HgO + 181.7kJ 2Hg + O2
Conservation of Energy• The law of____________________
states in exothermic and endothermic reactions the total amount of energy before and after the reaction is the same.
Homework • 7-3 Section Review page 209• Numbers 1,2,3
Ticket Out the Door• Please explain in a few sentences
how melting is an example of an endothermic reaction
7-4 Reaction Rates• A ________________ is the rate at
which reactants change into products over time.
• Reaction rates tell you how_______ a reaction is going
Factors Affecting Reaction Rates
• Factors that affect reaction rates include:1. ___________, 2. _____________, 3. _____________ 4. _____________5. ______________• Involve ___________ between particles• Reaction rate depends on how often these
particles _________
Temperature• An_________ in temperature will
_________the reaction rate• Ex. Frying an egg• ________ the temp will ________ the
reaction rate.• Ex: refrigerating milk to prevent spoiling• Increasing the ________, increases the
number of collisions between the particles, then _________ increases
Surface Area• The ________ the particle size of a given
mass, the _______ is its surface area.• An increase in _________ increases the
__________ of reactants to one another.• The __________this exposure, the more
collisions there are that involve reacting particles.
• ________ the surface area of a reactant tends to__________ the reaction rate.
Beaker Breaker• A__________rate is the rate at which
reactants change into products over time
• List two factors that affect reaction rates:
• An __________ in temperature will_________ the reaction rate
Stirring• You can ____________ the exposure of
reactants to each other by _________• Ex: washing machine• Stirring _____________ the reaction.• ____________ between the particles of
the reactants are more likely to happen
Concentration• _____________ refers to the number of
particles in a given volume• Ex: concentrated dyes• The reaction rate is ___________• For gases, concentration changes
with_______________ of a gaseous reactant, the __________ is its concentration, and the_________ the reaction rate.
Catalysts• A ___________ is a substance that affects
the reaction rate without being used up in the reaction.
• Chemists use catalysts to____________ a reaction or enable a reaction to occur at ___________ temperatures.
• Since the catalyst is neither a reactant nor a product, it is written ________ the arrow.
7-5 Equilibrium• _____________ is a state in which the
forward and reverse paths of change can take place at the ________ rate.
• Recall that changes to matter are either physical or chemical.
• When ___________ chemical changes take place at the same rate, a chemical equilibrium is reached
Physical Equilibrium• When a __________ change does
not go to completion, a physical equilibrium is established between the forward and reverse changes
• Ex: H2O (l) H2O(g)_________and___________are both
physical changes
Chemical Equilibrium• A ___________ reaction is a reaction in
which the conversion of reactants into products and the conversion of products into reactants can happen simultaneously
• When a chemical reaction does not go to completion, a ________________ is established between the forward and reverse reactions.
• Ex: 2SO2 (g) + O2 2SO3 (g) • Synthesis and decomposition
Factors Affecting Chemical Equilibrium
• When a change is introduced to a system in equilibrium, the equilibrium shifts in the direction that ________ the change.
• Principle was created by__________________
• Ex: N2 + 3H2 2NH3 + Heat
Temperature• N2 + 3H2 2NH3 + Heat• Synthesis of ammonia, heat is written
as a product• Forward reaction is ___________• Reverse is decomposition and is
____________•
Adding heat would then favor the______________reaction, which is endothermic
Pressure• __________ the pressure of the system,
equilibrium would shift in the direction that __________ the pressure of the system.
• Decreasing the pressure, the system would favor the reaction that produces__________gas molecules.
• Left Side has 4 gas molecules and right side has 2, so equilibrium would shift to the ________ when increasing the pressure
Concentration• Removing ammonia from the
system, Le Chatelier’s principle says that the equilibrium would shift in the direction that_________ ammonia
• In order to produce ammonia, the system would favor the __________reaction
Complete the following• Page 219 # 1,2,3,4, 5,