1. Chapter 9
Chemical
Reactions

2. Chemical reaction
process by which the atoms of one or more substances are rearranged to form different substances
same as chemical change

3. Chemical reaction
starting substances are reactants
substances formed or produced during reaction are products

4. Evidence of a chemical reaction (change)
1. temperature change
2. color change
production of a gas
(odor/bubbles)
4. formation of a solid
(precipitate)

5. Chemical equation
A statement using chemical formulas to describe the identities and relative amounts of the reactants and products involved in the chemical reaction.

8. Silver metal reacts with
hydrogen sulfide gas in the
air to form solid silver
sulfide and hydrogen gas.

9. Some pure elements exist as diatomic molecules.
H2, N2, O2, F2, Cl2, Br2, I2

10. -gens
hydrogen
oxygen
nitrogen
halogens (group 17)

11. Write formulas / symbols for the following:
magnesium
nitrogen
carbon dioxide
fluorine
sodium chloride
sulfur

12. Law of Conservation of Mass
Mass is neither created nor destroyed during a chemical reaction – it is conserved.
Total mass of reactants always equals total mass of products.

13. Therefore, chemical equations must be balanced; same number of atoms of each element on each side of arrow.

14. To balance a chemical equation:
Count number of
atoms of each
element on each
side of arrow.

15. Add coefficients in
front of formulas.
Must be lowest whole
number ratio.

16. Iron metal reacts with oxygen gas to form iron(III) oxide (rust.)

17. Classifying chemical reactions
useful for understanding chemical reactions and for predicting products
five general types of reactions

18. Synthesis reactions
two or more substances react to form a single product
A + B  AB
Key: one product

20. Synthesis reaction
Zinc metal reacts with solid iodine to form solid zinc iodide.

21. Decomposition reactions
a single compound breaks down into two or more simpler substances (elements or compounds)
AB  A + B
Key: one reactant

22. Decomposition reactions
often must add energy (heat/electricity) to make reaction occur

23. Decomposition reaction
When heated, solid potassium chlorate reacts to form solid potassium chloride and oxygen gas.

24. Single-replacement reactions
one element replaces another element in a compound
A + BX  AX + B

25. Single-replacement reactions
more active element replaces less active element

27. When balancing replacement reactions: keep polyatomic ions intact and write water as HOH (hydrogen and a hydroxide.)

28. Single-replacement reaction
Copper metal reacts with aqueous silver nitrate to produce silver metal and aqueous copper(II) nitrate.
copper replaces silver

30. Single-replacement reaction
Sodium metal reacts with water to form sodium hydroxide and hydrogen gas.

31. Double-replacement reactions
Exchange of ions between aqueous solutions of two compounds.
AX + BY  AY + BX

32. Double-replacement reactions
Aqueous solutions of lead(II) nitrate and potassium iodide react to form aqueous potassium nitrate and a precipitate of lead(II) iodide.

33. Combustion reactions
substance reacts rapidly with oxygen gas and releases energy in form of heat and light
may also be synthesis reaction

35. Iron metal reacts with oxygen gas to form iron(III) oxide (rust.)

36. Iron metal burns in oxygen gas to form iron(III) oxide.

37. Combustion reactions
If reactant contains carbon, then products of a combustion reaction are always carbon dioxide gas and water vapor.

38. Sucrose (C12H22O11) burns in oxygen.
Products are carbon dioxide gas and water vapor.

39. Single-replacement reactions
more active element replaces less active element

41. A more active metal will replace a less active metal.
Will the following single-replacement reaction occur?
Fe(s) + Cu(NO3)2(aq) 
Yes, iron is more active than copper.

42. Fe(s) + Cu(NO3)2(aq) 
Cu(s) + Fe(NO3)2(aq)

43. A more active nonmetal will replace a less active nonmetal.
Will the following single-replacement reaction occur?
Cl2(g) + NaBr(aq) 
Yes, chlorine is more active than bromine.

44. Cl2(g) + 2NaBr(aq) 
Br2(g) + 2NaCl(aq)

45. Will the following single-replacement reaction occur?
Al(s) + MgCl2(aq) 
No, aluminum is not more active than magnesium.

46. Solid calcium metal
reacts with water
to produce aqueous
calcium hydroxide
and hydrogen gas.

47. When aqueous solutions
of sulfuric acid and barium chloride are mixed, a precipitate of barium sulfate
and aqueous hydrochloric acid are formed.