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Chemical Equations
Name: __________________________________________Period: _____Date:_________
Part I: Parts and Meaning of a Chemical Equation:
1) _____________________________________= process by which one or more substances are
changed into one or more different substances (atoms are rearranged)
a) _____________________= original substances(written to the left of the arrow in a chemical
equation)
b) ________________________ = resulting substances(written to the right of the arrow in a
chemical equation)
________
_____
_
CH4 + 2O2
_________
_
CO2 + 2H2O
c) Indications of a chemical reaction (chemical change):
• evolution of ____________ and/or ___________
• production of a ____________ (often seen as bubbles)
• __________________________
• formation of a _________________________when two solutions are mixed
(Precipitate = a solid that separates from a solution)
d) __________________________ = a substance that speeds up a chemical reaction but is not
permanently consumed in the reaction.
•
Catalysts DO NOT appear as reactants or products!
•
Ex: manganese dioxide is a catalyst in the following reaction:
o 2H2O2
MnO2
O2 + 2H2O
1
A. Writing a Chemical Equation:
1) __________________________= a representation of the reactants and products in a chemical
reaction
a) ___________________________________ = a chemical equation in which the reactants
and products in a chemical reaction are represented by words
• Ex:
sodium + water → sodium hydroxide + hydrogen
__________________
__________________
b) _________________________________ = a chemical equation in which the reactants and
products in a chemical reaction are represented by chemical symbols or chemical
formulas
• Ex:
Na + H2O → NaOH + H2
reactants
products
c) ________________________ = whole number that appears to the right and below a
chemical symbol in a chemical formula (if no number is written it is assumed to be “1”)
• Indicates the number of ________________ or ______________________
• Ex: H2O
subscript
subscript (assumed to be “1”)
d) __________________________ = whole number that appears in front of a reactant or
product in a balanced chemical equation (if no number is written it is assumed to be
“1”)
• Indicates the number of molecules or moles
• Ex:
2 CO2
coefficient
• Ex:
Al2S3
coefficient (assumed to be “1”)
2
e) ______________________________________________________= a formula equation where
coefficients are added so equal numbers of each type of atom (ion) are represented on
each side of the equation
• Ex:
2 Na (s)
+
2 H2O (l)
→
2 NaOH (aq)
reactants
+
H2 (g)
products
• _____ molecules of solid sodium reacts with _____ molecules of water to yield ___
•
molecules of aqueous sodium hydroxide and _____ molecule of hydrogen gas.
OR
_____ moles of solid sodium reacts with ____ moles of water to yield ___ moles of
aqueous sodium hydroxide and ____ mole of hydrogen gas.
2) In the chemical equation below, identify the reactants, products, subscripts, and coefficients
4 Fe + 3 O2 → 2 Fe2O3
•
What are the reactant(s)?= ___________________________
•
What are the product(s)? = _____________________________
•
# of moles of O2 =__________________
•
# of molecules of O2=_______________
•
# of atoms of Fe in 2 Fe2O3 = _______________
•
# of atoms of O in 3 O2 =_____________
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3) Symbols you may see in a chemical equation:
Symbol
Meaning
“yields”; indicates result of a reaction
Indicates a reversible reaction
A reactant or product in the solid state
Alternative to (s); used only for a precipitate (solid) falling out of solution
A reactant or product in the liquid state
A reactant or product in aqueous solution (dissolved in water)
A reactant or product in the gaseous state
Alternative to (g); used only for a gaseous product
Reactants are heated
Pressure at which the reaction is carried out, in this case 2
Temperature at which reaction is carried out, in this case O°C
A catalyst is used to speed up the reaction rate, in this case MnO2 would be used
to speed up the reaction rate.
Part II: Requirements for Chemical Equations:
1) The equation must represent the known facts with all reactants and products identified.
2) The equation must contain the correct formulas of the reactants and products.
3) A chemical reaction obeys the “Law of Conservation of Matter”
• ____________________________________________________ = matter cannot
be either created or destroyed in ordinary chemical or physical means.
4) Why do we balance equations?
•
The ________________________________________________________must not be violated!
•
This means you must balance equations. (Equations are balanced by adding
_____________________________________, NOT subscripts.)
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5) Atomic theory can be used to explain why chemical reactions obey the “Law of Conservation
of Matter”.
•
_________ atoms present at the start of a chemical reaction are present at the end of
that chemical reaction (atoms are simply rearranged during a chemical reaction).
•
Since no atoms are created or destroyed in a chemical reaction no matter is created or
destroyed in a chemical reaction.
•
Since no matter is created or destroyed in the chemical reaction the mass of the
reactants must equal the mass of the products in a chemical reaction.
6) A _____________________ chemical equation details how a chemical reaction obeys the “Law of
Conservation of Matter”.
Part III: Information a Chemical Equation Does NOT
Supply:
1) Whether the reaction will actually____________. Chemical equations can be written for
reactions that do not necessarily take place.
2) The __________of a reaction.
3) The _____________________atoms or ions take in moving from reactants to products.
Part IV: Balancing Equations
1) Write a word equation
2) Write a formula equation
a) remember naturally occurring ___________________ molecules:
•
__________________________________
b) unless otherwise noted, other elements are represented by the element
symbol; ex: magnesium = Mg
• Ex: 2 Mg + O2
2MgO
c) remember the formulas for acids:
• HCl = Hydrochloric Acid
• H2CO3 = Carbonic Acid
• HNO3 = Nitric Acid
• H2SO4 = Sulfuric Acid
• H3PO4 = Phosphoric Acid
• CH3COOH = Acetic Acid(NOTE: the positive ion (H+) is at the end)
d) remember the rules for writing formulas for ionic compounds (________)
• Metals and Nonmetals!
e) remember the rules for writing formulas for molecular compounds (______________)
• Only NONMETALS!
f) remember the formula for water, ________
• HOH = hydrogen hydroxide
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3) Write a balanced chemical equation by adding_____________________, NOT subscripts (this
will require trial and error, the following guidelines may be helpful)
a) balance the different types of atoms ________________
b) first, balance the atoms of elements that are combined and that appear only
___________on each side of the equation
c) balance ____________________________that appear on both sides of the equation as
single units
d) balance H atoms and O atoms after atoms of all other elements have been balanced
4) Conduct an atom inventory throughout the process.
a. _________________________________________ (for a chemical equation) = a
“bookkeeping” technique designed to count the number of each type of atom (ion)
represented on each side of a chemical equation.
5) Be certain that the coefficients represent the ______________________________possible whole
number ratio of reactants and products.
Ex: 4 K + 2 Cl2
4 KCl (All coefficients can be reduced!)
2 K + 1 Cl2
2 KCl (Correct! -Shows reduction)
6) Common problems when balancing equations:
a) You must write correct formulas!
b) Once a correct formula is written, _____________________CANNOT be changed!
c) Don’t forget about the naturally occurring ________________________________ molecules:
H2, O2, N2, Cl2, Br2, I2, F2
7) For each of the following, write a formula equation and a balanced chemical equation.
a) Hydrogen reacts with oxygen to produce water.
b) Zinc reacts with hydrochloric acid to produce a solution of zinc chloride and hydrogen gas.
c) Aluminum sulfate reacts with calcium hydroxide to form aluminum hydroxide and calcium sulfate.
d) Nitrogen reacts with hydrogen to form ammonia (NH3)
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Chemical Equations Worksheet
1) Which side of the yields arrow do you find reactants? ______________________________
2) Which side of the yields arrow do you find products? _______________________________
3) In a chemical equation, what do the coefficients represent? ______________________________
4) In a chemical equation, what do the subscripts represent? ______________________________
5) How many atoms of chlorine are present in 2AlCl3 =__________________
6) How many moles of aluminum chloride are present in 2AlCl3 =__________________
7) How many atoms of aluminum are present in 2AlCl3 =__________________
8) How many molecules of aluminum chloride are present in 2AlCl3 =_____________
9) Why do we balance chemical equations?
10) What do the following symbols represent when used in a chemical equation?
a) H2
= _________________________________________________________________________
b) Ca(OH)2
= _____________________________________________________________________
c) MgSO4 (s) = _____________________________________________________________________
d) O2 (g) = ________________________________________________________________________
e) H2O (l) = ________________________________________________________________________
f) NaCl (aq) = ______________________________________________________________________
g) NaCl (l) = _______________________________________________________________________
11) What do the following symbols involving the yields arrow indicate?
∆
a) 2Mg + O2
2MgO __________________________________________________________
b) 2H2 + O2
2H2O ____________________________________________________________
c) C3H6 + H2 80°C C3H8 ____________________________________________________________
d) N2 + 3H2
Fe
2NH3
___________________________________________________________________________________________
12) List the naturally occurring diatomic molecules. _______________________________________________
13) Balance the following chemical equations.
a) ___ P4 + ___ O2
___ P2O3
b) ___ Na3PO4 + ___ KOH
___ NaOH + ___ K3PO4
c) ___ MgF2 + ___ Li2CO3
___ MgCO3 + ___ LiF
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Practice Balancing Equations
For each of the following, write a formula equation and balance the equation. If no additional
coefficients are needed, write “balanced”. Don’t forget about the diatomic molecules!
1. zinc + silver nitrate
zinc nitrate + silver
2. barium chloride + sodium sulfate
3. copper + nitrogen
barium sulfate + sodium chloride
copper (II) nitride
4. magnesium + sulfuric acid
magnesium sulfate + hydrogen
5. barium nitrate + ammonium chloride
6. potassium + water
barium chloride + ammonium nitrate
potassium hydroxide + hydrogen
7. fluorine + aluminum oxide
8. lithium + phosphoric acid
aluminum fluoride + oxygen
lithium phosphate + hydrogen
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9. aluminum + hydrochloric acid
10. nickel + nitric acid
aluminum chloride + hydrogen
nickel(II) nitrate + hydrogen
11. sodium chloride + lead(II) nitrate
12. magnesium + chlorine
13. iron + oxygen
magnesium chloride
iron(III) oxide
14. water + magnesium nitrate
15. sodium oxide + water
16. iron + copper(II) nitrate
17. calcium + water
lead(II) chloride + sodium nitrate
magnesium oxide + nitric acid
sodium hydroxide
iron(II) nitrate + copper
calcium hydroxide + hydrogen
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18. chlorine + lithium iodide
19. aluminum oxide
lithium chloride + iodine
aluminum + oxygen
20. carbon + iron(III) oxide
21. aluminum + zinc chloride
iron + carbon dioxide
aluminum chloride + zinc
22. mercury(II) sulfide + calcium oxide
23. bromine + water + sulfur dioxide
calcium sulfide + mercury(II) oxide
hydrogen bromide + sulfuric acid
24. diphosphorus pentaoxide + barium oxide
25. silver acetate + sodium phosphate
26. tin + potassium hydroxide
barium phosphate
silver phosphate + sodium acetate
potassium tin(II) oxide (K2SnO2) + hydrogen
10
Part V: Types of Reactions & Predicting Products:
1. ____________________: (S)
• 2 or more substances (A and B) react to produce a SINGLE product (AB)
• General format: A + B
AB
Ex:
NH3 + HCl
2 Na + C12
NH4Cl
2 NaCl
Synthesis Practice: For each of the following, predict the products and write a word equation.
Next, write a formula equation and a balanced chemical equation. Finally, write the type of
reaction represented by each chemical equation.
a) magnesium + oxygen →
b) sodium + fluorine →
c) magnesium + fluorine →
d) lithium + chlorine →
e) barium + oxygen →
f) potassium + oxygen →
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2. __________________________________: (D) – the opposite of synthesis
• A SINGLE compound breaks up or decomposes into simpler substances
• General format: AB
A + B
Ex: H2CO3
H2O + CO2
2 Al2O3
4 Al + 3 O2
Decomposition Practice: For each of the following, predict the products and write a word
equation. Next, write a formula equation and a balanced chemical equation. Finally, write the
type of reaction represented by each chemical equation.
a) water →
b) mercury(II) oxide →
c) magnesium chloride →
d) silver oxide →
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3. _________________________________________________: (SD)
• Element (A) + compound (BC) yields new compound (AC) + a new element (B)
• One element replaces another element in a compound
• General format: A + BC
AC + B
Ex: Cl2 + 2 KBr
2 KCl + Br2
2 Na + 2 H2O
2 NaOH + H2
Single Displacement Practice: For each of the following, predict the products and write a word
equation. Next, write a formula equation and a balanced chemical equation. Finally, write the
type of reaction represented by each chemical equation.
a) aluminum + lead(II) nitrate →
b) lithium + water →
c) aluminum + sulfuric acid →
d) chlorine + potassium bromide →
e) aluminum + silver nitrate →
f) barium + water →
g) lithium + hydrochloric acid →
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4. ____________________________________________________: (DD)
• Positive and negative ions are exchanged
• General format: AB + CD
CB + AD
Ex: Ba(OH)2 + H2SO4
BaSO4 + 2 H2O
AgNO3 + NaCl
AgCl + NaNO3
Double Displacement Practice: For each of the following, predict the products and write a word
equation. Next, write a formula equation and a balanced chemical equation. Finally, write the
type of reaction represented by each chemical equation.
a) potassium iodide + lead(II) nitrate →
b) acetic acid + sodium hydroxide →
c) nitric acid + potassium hydroxide
d) sulfuric acid + potassium hydroxide
e) calcium phosphate + acetic acid
f) Identify the following types of chemical reactions (S, D, SD, DD):
__________________
1) 2 H2O2
2 H2O +O2
__________________
2) 4 Fe + 3 02
__________________
3) Cl2 + 2 NaBr
2 NaCl + Br2
__________________
4) Zn + H2SO4
ZnSO4 + H2
__________________
5) Pb(NO3)2 + K2CrO4
2 Fe2O3
PbCrO4 + KNO3
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Predicting Products of Chemical Reactions SUMMARY
TYPE OF REACTION
REACTANTS
PRODUCTS
GENERIC EQUATION
Synthesis (S)
2 or more substances
ONE compound
Decomposition (D)
ONE compound
2 or more elements
and/or compounds
Single Displacement
(SD)
Element + Compound
New compound &
new element
A + BC
Double Displacement
(DD)
Compound + Compound
2 new compounds
AB + CD
A +B
AB
AB
A + B
AC + B
AD + CB
Identify the following types of reactions & explain why for the first 4 questions.
1) 2 H2O2
MnO
2
2 H2O + O2 _______________________
a) Why?
2) Cu + 2 AgNO3 → 2 Ag + Cu(NO3)2 __________________________________
a) Why?
3) 4 Al + 3 S → 2 Al2S3
_______________________
a) Why?
4) Zn(NO3)2 + Na2CrO4 → ZnCrO4 + 2 NaNO3 _______________________
a) Why?
5) F2 + 2 LiBr → 2 LiF + Br2 _______________________
6) NH4NO3 → N2O + 2 H2O __________________________________
7) 2 SO2 + O2 → 2 SO3 __________________________________
8) BaO + H2O → Ba(OH)2
_______________________
9) Mg + H2SO3 → MgSO3 + H2
_______________________
10) 3 CuBr2 + Al2O3 → 3 CuO + 2 AlBr3 __________________________
15
Part VI: Reaction Rates
1) _____________________________ = the rate (speed) of disappearance of a reactant or the rate of
appearance of a product in a chemical reaction
a) A chemical reaction that takes a long time to happen has a slow reaction rate.
b) A chemical reaction that takes a short time to happen has a fast reaction rate.
A.
Factors Affecting Reaction Rate
1) ______________________________________
a) Reactions occur at different rates depending on the reactants.
b) Some reactions occur almost instantaneously (such as double-replacement reactions).
c) Other reactions occur slower.
2) __________________________________ = a measure of the number of particles of matter per
unit volume
a) An increase in the concentration of the reactants generally increases reaction rate.
b) A decrease in the concentration of the reactants generally decreases reaction rate.
3) __________________________________ = a measure of the average kinetic energy of the
particles in a sample of matter
a) An increase in temperature increases reaction rate.
b) A decrease in temperature decreases reaction rate.
4) Presence of a __________________________= a substance that increases the rate of a chemical
reaction without being permanently changed
a) A catalyst will increase reaction rate.
b) A catalyst is __________ permanently changed in a chemical reaction.
B.
Collision Theory
1) Assumptions of collision theory:
a) Reacting molecules must ____________ with each other.
b) Reacting molecules must collide with sufficient ______________.
c) Reacting molecules must collide in an orientation that can lead to
________________________ of the atoms.
16
2) Use collision theory to explain why an increase in CONCENTRATION increases reaction
rate:
a) At a _______________ concentration ____________ reactant molecules are present.
b) When more reactant molecules are present more frequent __________________ occur.
c) When more frequent collisions occur there are more chances for molecules to react (so
reactions happen ___________________).
3) Use collision theory to explain why an increase in TEMPERATURE increases reaction
rate:
a) Molecules with a higher kinetic energy move faster, collide more often, and have more
energetic collisions.
b) A higher temperature means that the average kinetic energy of the reacting molecules
is _____________________; at a higher temperature there are more molecules with a
higher kinetic energy.
c) At a higher temperature there are____________________________________________
giving molecules more chances to react (so reactions happen faster).
d) At a higher temperature, more molecules possess enough kinetic energy to react so a
higher percentage of collisions result in molecules reacting (so reactions happen faster).
17
Practice Predicting Products, Balancing Equations, and Types of Reactions
For each of the following, predict the products and write a word equation. Next, write a formula
equation and a balanced chemical equation. Finally, write the type of reaction represented by
each chemical equation on the line next to the number.
____1. zinc + sulfur
____2. potassium + water
____3. calcium + nitric acid
____4. silver oxide
____5. hydrochloric acid + sodium hydroxide
____6. sodium sulfate + calcium nitrate
____7. zinc chloride + ammonium oxide
18
____8. zinc + copper(II) acetate
____9. sodium + sulfuric acid
____10. calcium + water
____11. sulfuric acid + potassium hydroxide
____12. chlorine + potassium bromide
____13. zinc + hydrochloric acid
____14. aluminum + iron(III) oxide
19
____15.
copper (II) acetate + potassium permanganate
____16.
calcium peroxide
____17.
copper (II) sulfide + barium iodide
____18.
iron (III) nitrate + sodium hydroxide
____19.
nitric acid + aluminum hydroxide
____20.
sodium + oxygen
____21.
lithium + hydrochloric acid
____22.
potassium nitrate + zinc peroxide
20
Review Worksheet:
Answer the questions 1-8, using this equation:
2 Na (s) + 2 H2O (l)
2 NaOH (aq) + H2
1. What are the reactant(s)? _____________________
2. What are the product(s)? _______________________
3. How many molecules of H2 are present as a product? ___________
4. How many moles of NaOH are present? ____________
5. How many atoms of H are present in 2 H2O? __________
6. What molecule or compound is a gas? __________________
7. What element or compound was dissolved in water? _________________
8. What element or compound is a solid? _________________
9. Why do we balance equations?
10. How do you correctly notate that heat is needed in the following equation, in order to produce
the product?
2 Cu + O2
2 CuO
11. List the diatomic molecules.
_____________________________________________________________
12. What is a catalyst?
13. Write the formulas for the following acids:
a) Carbonic Acid = ______________________________
b) Nitric Acid = ______________________________
c) Sulfuric Acid = ______________________________
d) Phosphoric Acid = ______________________________
e) Hydrochloric Acid = ______________________________
f) Acetic Acid = ______________________________
21
14. List the 4 indicators that a chemical reaction occurred.
15. What is a reaction rate?
16. What are four factors that affect the reaction rate?
17. Using collision theory, EXPLAIN why increasing the concentration, increases the reaction
rate?
18. Using collision theory, EXPLAIN why increasing the temperature, increases the reaction
rate?
_______ 19. chlorine + potassium iodide
_______ 20. magnesium hydroxide + hydrochloric acid
_______ 21. zinc + potassium dichromate
_______ 22. potassium + chlorine
‘
_______ 23. mercury(II) oxide
_______ 24. copper(II) sulfate + zinc
22
Unit Learning Map (10 days):
Chemical Reactions/Equations
Mrs. Hostetter
Class:
Chemistry B – PA standard: Describe factors that influence the frequency of collisions during chemical
reactions that might affect the reaction rates.
Instructional Tools:
Unit Essential Question(s):
Guided Notes
Lab Materials:
Models of Chemical Reactions
Chemical Reactions and
What are chemical reactions
and how are they represented?
Concept:
Writing Word Equations,
Formula Equations, and
Balanced Chemical Equations
Lesson Essential Question(s):
1) How is a chemical
reaction represented?
2) Given a description of
a chemical reaction,
how are a word
equation and a formula
equation written?
3) How is a formula
equation balanced by
trial and error?
Vocabulary:
Chemical reaction
(chemical change)
Reactant
Product
Indications of a chemical
reaction
Chemical symbol
Chemical formula
Chemical equation
Word equation
Formula equation
Atom inventory
Subscript
Coefficient
Balanced chemical equation
Concept:
Balanced Chemical
Equations
Lesson Essential Question(s):
1)
2)
3)
How can atomic theory be
used to explain why
chemical reactions obey
the “Law of Conservation
of Matter”?
How are balanced
chemical equations
translated into sentences?
What information is
given/not given by a
balanced chemical
equation?
Vocabulary:
Law of conservation of
Matter
Atomic theory
Atom
Molecule
Formula unit
Catalyst
Symbols in a chemical
equation
Chemical Equations
Reaction Rates
Chemistry Competition
Concept:
Types of Chemical
Reactions and Predicting
Products
Lesson Essential Question(s):
1) How can synthesis,
decomposition, singledisplacement, and
double-displacement
reactions be recognized
and described?
2) Given the reactants,
how can the products
of simple chemical
reactions be predicted?
Vocabulary:
Synthesis reaction
Decomposition reaction
Single-displacement
reaction
Double-displacement
reaction
Concept:
Reaction Rates
Lesson Essential Question(s):
1)
2)
What effect do nature of
reactants, concentration,
temperature, and
presence of a catalyst
have on reaction rate?
How can collision theory
be used to explain why
concentration and
temperature affect
reaction rate as they do?
Vocabulary:
Reaction rate
Concentration
Temperature
Catalyst
Collision theory
23
Chemical Equations Vocabulary:
1) Chemical reaction = process by which one or more substances are changed into one or more different
substances (atoms are rearranged)
2) Reactants = original substances(written to the left of the arrow in a chemical equation)
3) Products = resulting substances(written to the right of the arrow in a chemical equation)
4) Indications of a chemical reaction (chemical change): evolution of heat and/or light; production of a gas
(often seen as bubbles); color change; formation of a precipitate when two solutions are mixed
5) Precipitate = a solid that separates from a solution
6) Catalyst = a substance that speeds up a chemical reaction but is not permanently consumed in the reaction
7) Chemical equation = a representation of the reactants and products in a chemical reaction
8) Word equation = a chemical equation in which the reactants and products in a chemical reaction are
represented by words
9) Formula equation = a chemical equation in which the reactants and products in a chemical reaction are
represented by chemical symbols or chemical formulas
10) Atom inventory = a “bookkeeping” technique designed to count the number of each type of atom (ion)
represented on each side of a chemical equation
11) Subscript = whole number that appears to the right and below a chemical symbol in a chemical
12) Coefficient = whole number that appears in front of a reactant or product in a balanced chemical equation
(if no number is written it is assumed to be “1”)
13) Balanced chemical equation = a formula equation where coefficients are added so equal numbers of each
type of atom (ion) are represented on each side of the equation
14) The Law of Conservation of Matter = matter cannot be either created or destroyed in ordinary chemical or
physical means
15) Synthesis(S) = 2 or more substances combine to form a SINGLE product; General format: A + B → AB
16) Decomposition (D) = the opposite of synthesis; Single substance breaks up or decomposes into simpler
substances; General format: AB → A + B
17) Single Displacement(SD) = One element replaces another element in a compound;
General format: A + BC → AC + B
18) Double Displacement(DD) = Positive and negative ions are exchanged;
General format: AB + CD → CB + AD
19) Reaction rate = the rate (speed) of disappearance of a reactant or the rate of appearance of a product in a
chemical reaction
20) Concentration = a measure of the number of particles of matter per unit volume
21) Temperature = a measure of the average kinetic energy of the particles in a sample of matter
22) Assumptions of collision theory = a) Reacting molecules must collide with each other b) Reacting
molecules must collide with sufficient energy c) Reacting molecules must collide in an orientation that can
lead to rearrangement of the atoms
24