1. CHAPTER 10
Chemical Reactions
10.1 Chemical Equations

2. The alphabet of chemistry
More than 200,000 words in the English language
Trillions of substances
that make up the universe

3. The language of chemistry
Element symbols
H, O, Na, Fe
Alphabet
of chemistry

4. The language of chemistry
Element symbols
H, O, Na, Fe
Compound formulas
H2O, CO2, NaCl
Alphabet
of chemistry
Words

5. The language of chemistry
Element symbols
H, O, Na, Fe
Compound formulas
H2O, CO2, NaCl
Chemical equations
2H2 + O H2O
Alphabet
of chemistry
Words
Sentences

6. Chemical reactions tell a story
Chemical equations
2H2 + O H2O
Sentences
of chemistry
Reactants Products
Chemical reactions tell a story
chemical equation: an expression that describes the changes that happen in a chemical reaction.

7. Consider one reaction that takes place in a fire:

8. Consider one reaction that takes place in a fire:
Carbon (from wood) reacts with oxygen (from the atmosphere)
to produce carbon dioxide gas

9. Consider one reaction that takes place in a fire:
carbon oxygen
Carbon (from wood) reacts with oxygen (from the atmosphere)
to produce carbon dioxide gas

10. Consider one reaction that takes place in a fire:
carbon oxygen carbon dioxide
Carbon (from wood) reacts with oxygen (from the atmosphere)
to produce carbon dioxide gas

11. Consider one reaction that takes place in a fire:
carbon oxygen carbon dioxide
C O CO2

12. Consider one reaction that takes place in a fire:
carbon oxygen carbon dioxide
C O CO2
Reactants Products

13. Consider one reaction that takes place in a fire:
carbon oxygen carbon dioxide
separates the reactants
arrow points toward the products
C O CO2
Reactants Products

14. Consider one reaction that takes place in a fire:
C O CO2
1 mole
1 mole
1 mole

15. Consider one reaction that takes place in a fire:
C O CO2
1 mole x
12 g/mole
1 mole x
32 g/mole
1 mole x
44 g/mole

16. Consider one reaction that takes place in a fire:
C O CO2
1 mole x
12 g/mole =
12 g
1 mole x
32 g/mole =
32 g
1 mole x
44 g/mole =
44 g

17. Consider one reaction that takes place in a fire:
C O CO2
1 mole x
12 g/mole =
12 g
1 mole x
32 g/mole =
32 g
1 mole x
44 g/mole =
44 g
Total mass of reactants
= 44 g
Total mass of products
= 44 g

18. Total mass of reactants
1 mole x
12 g/mole =
12 g
1 mole x
32 g/mole =
32 g
1 mole x
44 g/mole =
44 g
C O CO2
Total mass of reactants
= 44 g
Total mass of products
= 44 g

19. Reaction that fuels the space shuttle:
Hydrogen burns with oxygen to produce water
The “white smoke” is actually water vapor

20. Reaction that fuels the space shuttle:
Hydrogen burns with oxygen to produce water
hydrogen +
oxygen
water

21. Reaction that fuels the space shuttle:
hydrogen H2 +
oxygen O2
water
H2O

22. Reaction that fuels the space shuttle:
hydrogen H2 +
oxygen O2
water
H2O

23. Reaction that fuels the space shuttle:
hydrogen H2 +
oxygen O2
water
H2O
2 hydrogen atoms
2 oxygen atoms
2 hydrogen atoms
1 oxygen atom

24. Reaction that fuels the space shuttle:
hydrogen H2 +
oxygen O2
water
H2O
2 hydrogen atoms
2 oxygen atoms
2 hydrogen atoms
1 oxygen atom

25. This chemical equation is not balanced:
it violates the law of conservation of mass
Hydrogen H2 +
Oxygen O2
Water
H2O
2 hydrogen atoms
2 oxygen atoms
2 hydrogen atoms
1 oxygen atom

26. 2H2 From Chapter 4.2 Subscript tells how many atoms in 1 molecule
Hydrogen gas

27. 2H2 From Chapter 4.2 Coefficient tells how many molecules are involved
Hydrogen gas

28. 2H2 From Chapter 4.2 Coefficient tells how many molecules are involved
Subscript tells how many atoms in 1 molecule
Hydrogen gas
When balancing a chemical equation, only coefficients can be changed
Subscripts remain the same

29. 2H2 O2 3H2O Coefficients 2 hydrogen molecules 1 oxygen molecule
Atoms
2 hydrogen molecules
1 oxygen molecule
3 water molecules
2H2 O2
3H2O

30. 2H2 O2 3H2O Coefficients 2 hydrogen molecules 1 oxygen molecule
Atoms
2 hydrogen molecules
1 oxygen molecule
3 water molecules
2H2 O2
3H2O

31. 2H2 O2 3H2O Coefficients 2 hydrogen molecules 1 oxygen molecule
Atoms
2 hydrogen molecules
1 oxygen molecule
3 water molecules
2H2 O2
3H2O

32. 2H2 + O2 2H2O The balanced chemical equation: Reactants Products
Molecules
Atoms

34. The glucose (C6H12O6) contained in biomass is used as biofuel to produce (C2H6O) and carbon dioxide (CO2). Write the balanced equation for this reaction.

35. The glucose (C6H12O6) contained in biomass is used as biofuel to produce (C2H6O) and carbon dioxide (CO2). Write the balanced equation for this reaction.
Asked: The coefficients needed to balance the chemical equation
Given: The unbalanced chemical equation C6H12O6 → C2H6O + CO2
Relationships: The same number of each type of atom must appear on each side.

36. The glucose (C6H12O6) contained in biomass is used as biofuel to produce (C2H6O) and carbon dioxide (CO2). Write the balanced equation for this reaction.
Asked: The coefficients needed to balance the chemical equation
Given: The unbalanced chemical equation C6H12O6 → C2H6O + CO2
Relationships: The same number of each type of atom must appear on each side.
Solve: All atoms involved in the reaction are unbalanced. There are 6 C atoms, 12 H atoms, and 6 O atoms in the reactants. There are 3 C atoms, 6 H atoms, and 3 O atoms in the products. From this accounting, we notice that the number of atoms in the products is half the number of atoms in the reactants.

37. The glucose (C6H12O6) contained in biomass is used as biofuel to produce (C2H6O) and carbon dioxide (CO2). Write the balanced equation for this reaction.
Asked: The coefficients needed to balance the chemical equation
Given: The unbalanced chemical equation C6H12O6 → C2H6O + CO2
Relationships: The same number of each type of atom must appear on each side.
Solve: All atoms involved in the reaction are unbalanced. There are 6 C atoms, 12 H atoms, and 6 O atoms in the reactants. There are 3 C atoms, 6 H atoms, and 3 O atoms in the products. From this accounting, we notice that the number of atoms in the products is half the number of atoms in the reactants. By multiplying the products by a factor of 2 we obtain a balanced chemical equation of the reaction.

38. The glucose (C6H12O6) contained in biomass is used as biofuel to produce (C2H6O) and carbon dioxide (CO2). Write the balanced equation for this reaction.
Asked: The coefficients needed to balance the chemical equation
Given: The unbalanced chemical equation C6H12O6 → C2H6O + CO2
Relationships: The same number of each type of atom must appear on each side.
Solve: All atoms involved in the reaction are unbalanced. There are 6 C atoms, 12 H atoms, and 6 O atoms in the reactants. There are 3 C atoms, 6 H atoms, and 3 O atoms in the products. From this accounting, we notice that the number of atoms in the products is half the number of atoms in the reactants. By multiplying the products by a factor of 2 we obtain a balanced chemical equation of the reaction.
Answer: The balanced chemical equation is C6H12O6 → 2C2H6O + 2CO2.

39. 2H2 Coefficient tells how many molecules are involved
When balancing a chemical equation, only coefficients can be changed
Subscripts remain the same
2H2
Subscript tells how many atoms in 1 molecule