Chapter 5Chemical Reactions and Quantities : LecturePLUS Timberlake 1 Chapter 5Chemical Reactions and Quantities Chemical Changes
Balancing Chemical Equations
Physical Properties : LecturePLUS Timberlake 2 Physical Properties color
melting point
boiling point
electrical conductivity
specific heat
density
state (solid, liquid, or gas)
Physical Change : LecturePLUS Timberlake 3 Physical Change Changes in physical properties
melting
boiling
condensation
No change occurs in the identity of the substance
Example:
Ice , rain, and steam are all water
Chemical Change : LecturePLUS Timberlake 4 Chemical Change Atoms in the reactants are rearranged to form one or more different substances
Old bonds are broken; new bonds form
Examples:
Fe and O2 form rust (Fe2O3)
Ag and S form tarnish (Ag2S)
Learning Check E1 : LecturePLUS Timberlake 5 Learning Check E1 Classify each of the following as a
1) physical change or 2) chemical change
A. ____ a burning candle
B. ____ melting ice
C. ____ toasting a marshmallow
D. ____ cutting a pizza
E. ____ polishing silver
Solution E1 : LecturePLUS Timberlake 6 Solution E1 Classify each of the following as a
1) physical change or 2) chemical change
A. __2__ a burning candle
B. __1_ melting ice
C. __2__ toasting a marshmallow
D. __1__ cutting a pizza
E. __2__ polishing silver
Chemical Reaction : LecturePLUS Timberlake 7 Chemical Reaction A process in which at least one new substance is produced as a result of chemical change.
A Chemical Reaction : LecturePLUS Timberlake 8 A Chemical Reaction Reactants Products
Learning Check E2 : LecturePLUS Timberlake 9 Learning Check E2 A. How does an equation indicate a change in
the identity of the reacting substances?
B. How did the yellow and green reactants
combine?
C. Did all the reactants form product? Why or
why not?
Learning Check E2 : LecturePLUS Timberlake 10 Learning Check E2 A. How does an equation indicate a change in
the identity of the reacting substances?
The formulas of the reactants are different
than the formulas of the products.
B. How did the yellow and green reactants
combine? 1 yellow combined with 1 green.
C. Did all the reactants form product? Why or
why not? No. There were more yellow
reactants than green.
Writing a Chemical Equation : LecturePLUS Timberlake 11 Writing a Chemical Equation Chemical symbols give a “before-and-after” picture of a chemical reaction
Reactants Products
MgO + C CO + Mg
magnesium oxide to form carbon monoxide
reacts with carbon and magnesium
Learning Check E3 : LecturePLUS Timberlake 12 Learning Check E3 12 oz of dough, 4 oz mushrooms, 12 slices pepperoni, 8 oz cheese and 5 oz tomato sauce are used to make a pizza. Write a recipe in words for putting together a pizza.
How would you write the recipe as an equation?
Solution E3 : LecturePLUS Timberlake 13 Solution E3 Example: Combine 12 oz dough + 4 oz mushrooms + 12 slices pepperoni + 8 oz cheese + 5 oz tomato sauce and heat 30 minutes at 350°C to produce 1 pizza
12 oz dough + 4 oz mshrm
+ 12 pep + 8 oz chse 1 pizza
+ 5 oz tom sauce
Reading A Chemical Equation : LecturePLUS Timberlake 14 Reading A Chemical Equation 4 NH3 + 5 O2 4 NO + 6 H2O
Four molecules of NH3 react with five molecules O2 to produce four molecules NO and six molecules of H2O
or
Four moles NH3 react with 5 moles O2 to produce four moles NO and six moles H2O
A Balanced Chemical Equation : LecturePLUS Timberlake 15 A Balanced Chemical Equation Same numbers of each type of atom on each side of the equation
Al + S Al2S3 Not Balanced
2Al + 3S Al2S3 Balanced
Matter Is Conserved : LecturePLUS Timberlake 16 Matter Is Conserved H2 + Cl2 2 HCl
+ +
Total atoms = Total atoms
2 H, 2 Cl 2H, 2 Cl
Total Mass = Total Mass
2(1.0) + 2(35.5) 2(36.5)
73.0 g = 73.0 g
Law of Conservation of Mass : LecturePLUS Timberlake 17 Law of Conservation of Mass In any ordinary chemical reaction, matter is not created nor destroyed
Balance Equations with Coefficients : LecturePLUS Timberlake 18 Balance Equations with Coefficients Coefficients in front of formulas balance each type of atom
4NH3 + 5O2 4NO + 6H2O
4 N = 4 N
12 H = 12 H
10 O = 10 O
Steps in Balancing An Equation : LecturePLUS Timberlake 19 Steps in Balancing An Equation Fe3O4 + H2 Fe + H2O
Fe: Fe3O4 + H2 3 Fe + H2O
O: Fe3O4 + H2 3 Fe + 4 H2O
H: Fe3O4 + 4 H2 3 Fe + 4 H2O
Learning Check E4 : LecturePLUS Timberlake 20 Learning Check E4 Fe3O4 + 4 H2 3 Fe + 4 H2O
A. Number of H atoms in 4 H2O
1) 2 2) 4 3) 8
B. Number of O atoms in 4 H2O
1) 2 2) 4 3) 8
C. Number of Fe atoms in Fe3O4
1) 1 2) 3 3) 4
Solution E4 : LecturePLUS Timberlake 21 Solution E4 Fe3O4 + 4 H2 3 Fe + 4 H2O
A. Number of H atoms in 4 H2O
3) 8
B. Number of O atoms in 4 H2O
2) 4
C. Number of Fe atoms in Fe3O4
2) 3
Learning Check E5 : LecturePLUS Timberlake 22 Learning Check E5 Balance each equation. The coefficients for each equation are read from left to right
A. Mg + N2 Mg3N2
1) 1, 3, 2 2) 3, 1, 2 3) 3, 1, 1
B. Al + Cl2 AlCl3
1) 3, 3, 2 2) 1, 3, 1 3) 2, 3, 2
Learning Check E5 : LecturePLUS Timberlake 23 Learning Check E5 C. Fe2O3 + C Fe + CO2
1) 2, 3, 2,3 2) 2, 3, 4, 3 3) 1, 1, 2, 3
D. Al + FeO Fe + Al2O3
1) 2, 3, 3, 1 2) 2, 1, 1, 1 3) 3, 3, 3, 1
E. Al + H2SO4 Al2(SO4)3 + H2
1) 3, 2, 1, 2 2) 2, 3, 1, 3 3) 2, 3, 2, 3
Solution E5 : LecturePLUS Timberlake 24 Solution E5 A. 3 Mg + N2 Mg3N2
B. 2 Al + 3 Cl2 2 AlCl3
C. 2 Fe2O3 + 3 C 4 Fe + 3 CO2
D. 2 Al + 3 FeO 3 Fe + Al2O3
E. 2 Al + 3 H2SO4 Al2(SO4)3 + 3 H2