1. Chemical Reactions and Quantities

2. Chemical Change In a chemical change,
reacting substances form new substances with different compositions and properties
a chemical reaction takes place

3. Evidence of Chemical Change

4. Chemical Reactions In a chemical reaction,
a chemical change produces one or more new substances
there is a change in the composition of one or more substances

5. Chemical Reactions (continued)
In a chemical reaction,
old bonds are broken and new bonds formed
atoms in the reactants are rearranged to form one or more different substances

6. Learning Check Identify the visible evidence of a chemical
reaction in each of the following:
1) Methane gas in an outdoor heater burns with a blue flame.
2) Bleach removes stains from a shirt.
3) Bubbles of CO2 are released when baking soda is mixed with vinegar.

7. Solution 1) Methane gas in an outdoor heater burns with a blue flame.
Heat and a flame
2) Bleach removes stains from a shirt.
Color change (color removed)
3) Bubbles of CO2 are released when baking soda is mixed with vinegar.
Formation of gas (bubbles)

8. Chemical Equations A chemical equation
gives the chemical formulas of the reactants on the left of the arrow and the products on the right

9. Symbols Used in Equations
Symbols used in chemical
equations show
the states of the reactants
the states of the products
the reaction conditions

10. Chemical Equations are Balanced
In a balanced chemical
reaction,
atoms are not lost or gained
the number of atoms in the reactants is equal to the number of atoms in the products

11. Equation for A Chemical Reaction

12. Checking a Balanced Equation

13. Guide to Balancing Equations

14. Balancing Chemical Equations
STEP 1 Write the equation with the correct formulas.
N2(g) + H2(g) NH3(g)
STEP 2 Determine if the equation is balanced.
No, not all of the atoms are balanced.
2N N
2H H
STEP 3 Balance with coefficients in front of formulas.
Balance N
N2(g) + H2(g) 2NH3(g)

15. Balancing Chemical Equations (continued)
STEP 3 (continued)
Balance H
N2(g) + 3H2(g) 2NH3(g)
STEP 4 Check that atoms of each element are equal in reactants and products.
2N = N
6H = H

16. Learning Check Check the balance of atoms in the following:
Fe3O4(s) + 4H2(g) Fe(s) + 4H2O(l)
A. number of H atoms in products
1) 2 2) 4 3) 8
B. number of O atoms in reactants
C. number of Fe atoms in reactants
1) 1 2) 3 3) 4

17. Solution Fe3O4(s) + 4H2(g) 3Fe(s) + 4H2O(l)
A. number of H atoms in products
3) 8 (4H2O)
B. number of O atoms in reactants
2) 4 (Fe3O4)
C. number of Fe atoms in reactants
2) 3 (Fe3O4)

18. Learning Check
Balance each equation and list the coefficients in the balanced equation going from reactants to products.
A. __Mg(s) + __N2(g) __Mg3N2(s)
1) 1, 3, 2 2) 3, 1, 2 3) 3, 1, 1
B. __Al(s) + __Cl2(g) __AlCl3(s)
1) 3, 3, 2 2) 1, 3, 1 3) 2, 3, 2

19. Equations with Polyatomic Ions

20. Chemical Reactions and Quantities
Types of Reactions

21. Types of Reactions Chemical reactions can be classified as
synthesis reactions
decomposition reactions
single replacement reactions
double replacement reactions

22. Synthesis Reaction In a synthesis reaction,
two or more elements (or simple compounds)
combine to form one product
2Mg(s) + O2(g) 2MgO(s)
2Na(s) + Cl2(g) 2NaCl(s)
SO3(g) + H2O(l) H2SO4(aq)

23. Formation of MgO

24. Decomposition Reaction
In a decomposition reaction,
one substance splits into two or more simpler substances
2HgO(s) 2Hg(l) + O2(g)
2KClO3(s) 2KCl(s) + 3O2(g)

25. Decomposition of HgO

26. Learning Check 1) synthesis or 2) decomposition
Classify the following reactions as:
1) synthesis or 2) decomposition
___A. H2(g) + Br2(g) HBr(l)
___B. Al2(CO3)3(s) Al2O3(s) + 3CO2(g)
___C. 4Al(s) + 3C(s) Al4C3(s)

27. Solution 1) synthesis or 2) decomposition 1 A. H2(g) + Br2(g) 2HBr(l)
Classify the following reactions as:
1) synthesis or 2) decomposition
1 A. H2(g) + Br2(g) HBr(l)
2 B. Al2(CO3)3(s) Al2O3(s) + 3CO2(g)
1 C. 4Al(s) + 3C(s) Al4C3(s)

28. Single Replacement Reaction
In a single replacement reaction,
one element takes the place of a different element in a reacting compound
Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)
Fe(s) + CuSO4(aq) FeSO4(aq) + Cu(s)

29. Zn and HCl Combine in a Single Replacement Reaction

30. Double Replacement Reaction
In a double replacement,
two elements in the reactants exchange places
AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
ZnS(s) + 2HCl(aq) ZnCl2(aq) + H2S(g)

31. Example of Double Replacement

32. Learning Check Classify each of the following reactions as:
1) single replacement or 2) double replacement
A. 2Al(s) + 3H2SO4(aq) Al2(SO4)3(aq) + 3H2(g)
B. Na2SO4(aq) + 2AgNO3(aq) Ag2SO4(s) + 2NaNO3(aq)
C. 3C(s) + Fe2O3(s) Fe(s) + 3CO(g)

33. Solution Classify each of the following reactions as:
1) single replacement or 2) double replacement
1 A. 2Al(s) + 3H2SO4(aq) Al2(SO4)3(aq) + 3H2(g)
2 B. Na2SO4(aq) + 2AgNO3(aq)
Ag2SO4(s) + 2NaNO3(aq)
1 C. 3C(s) + Fe2O3(s) Fe(s) + 3CO(g)

34. Learning Check Identify each of the following reactions as:
1) synthesis 2) decomposition
3) single replacement 4) double replacement
A. 3Ba(s) + N2(g) Ba3N2(s)
B. Hg(l) + 2HCl(aq) HgCl2(aq) + H2(g)
C. SiO2(s) + 4HF(aq) SiF4(g) + 2H2O(l)
D. PbCl2(aq) + K2SO4(aq) KCl(aq) + PbSO4(s)
E. K2CO3(s) K2O(s) + CO2(g)

35. Solution Identify each of the following reactions as:
1) synthesis 2) decomposition
3) single replacement 4) double replacement
1 A. 3Ba(s) + N2(g) Ba3N2(s)
3 B. Hg(l) + 2HCl(aq) HgCl2(s) + H2(g)
4 C. SiO2(s) + 4HF(aq) SiF4(g) + 2H2O(l)
4 D. PbCl2(aq) + K2SO4(aq) KCl(aq) + PbSO4(s)
2 E. K2CO3(s) K2O(s) + CO2(g)