Chemical Equations and Reactions

1
Chapter 8 Chemical Equations and
Reactions
NearingZero.Net
2
Chapter 8.1 Describing Chemical Reactions

• Parts of an equation
• Reactants Products
• Mg O2 MgO energy
• Word Equation
• Magnesium and oxygen yields magnesium oxide and
  energy
• pg 246 symbols used in Chemical Equations

Yields
3

• Chemical equation represents, with symbols and
  formulas, the identities and relative amounts of
  the reactants and products in a chemical
  reaction.
• Indications of a Chemical Reaction
• Evolution of heat and light
• Production of gas
• Formation of a precipitate.

4
Characteristics of Chemical Equations

• The equation must represent known facts
• The equation must contain correct formulas for
  the reactants and products
• The law of conservation of mass must be
  satisfied. (Balanced equation)

5

• Word equation -represents the reactants and
  products using words.
• Formula equation -represents the reactants and
  products using symbols or formulas.
• Balanced equation -is the formula equation with
  added coefficients to satisfy the law of
  conservation.

6

• Conservation of mass - atoms can be neither
  created or destroyed.
• The numbers of atoms of each element must be the
  same on both sides of the yields.
• No mass is lost or gained.

7
Balancing Equations

• H2 O2 H2O
• Hydrogen oxygen yields water (dihydrogen
  monoxide)
• H2 O2 H2O

• Write the word equation
• Make a T-chart
• Put the number of each element on the t-chart
• If the of atoms are not the same you need to
  balance. You can only add COEFFICIENTS (Big )
• Check work! Count all s of each element.

Left Right
H O
2 2
2 1
2
2
2 1
4 2
H O
2 2
4
8
8.2 Types of Chemical Reactions

• 5 types of reactions
• Synthesis
• Decomposition
• Single replacement
• Double replacement
• Combustion

9

• Synthesis
• A B C
• 2 or more simple substances combine to form a new
  complex substance.

• Decomposition
• C A B
• A complex substance breaks down into 2 or more
  simpler substances.

10

• Single Replacement
• A BX AX B
• An uncombined element replaces an element that is
  part of a compound.

• Double Replacement
• AX BY AY BX
• Different atoms in 2 different compounds replace
  each other.

Likes replace Likes
11
Combustion

• Hydrocarbons are compounds made up of carbon and
  hydrogen
• Hydrocarbon Oxygen Carbon Dioxide and
  Water

12
Slide 12-15Put on your note cards!!!

• Synthesis
• Reactions of elements with oxygen produces an
  OXIDE
• Reactions of two nonmetals forms a covalent
  compound
• Reactions of metals with nonmetals other than
  oxygen produces an ionic compound
• Oxides of active metals react with water to
  produce metal hydroxide.

13
Decomposition

1. Binary compounds breakdown into its elements.
2. Electrolysis-same as 1
3. Decomposition of metal carbonates to produce
   metal oxide and carbon dioxide
4. Decomposition of metal hydroxide to produce metal
   oxide and water
5. Decomposition of metal chlorates to produce metal
   chloride and oxygen
6. Decomposition of acids to produce water and
   whatever is left

14
Single Replacement

1. Replacement of a metal by a more reactive metal
2. Replacement of hydrogen in water by a metal to
   produce metal hydroxide and hydrogen
3. Replacement of hydrogen in an acid by a metal to
   produce hydrogen and metal compound
4. Replacement of halogens 1 halogen replaces
   another halogen.

15

• Double Replacement- Likes replace likes. Metals
  replace metals
• Combustion-always produce carbon dioxide and water

16
8.3 Activity Series of the Elements

• Activity series-is a list of elements organized
  according to ease with which the elements undergo
  certain chemical reactions.

17
React with cold water and acids, replacing
hydrogen. React with oxygen, forming oxides.
React with steam and acids, replacing hydrogen.
React with oxygen, forming oxides.
The higher up on the chart the stronger it
is!!!! King of the mountain
Do not react with water. React with acids,
replacing hydrogen. React with oxygen, forming
oxides.
React with oxygen, forming oxides.
Fairly unreactive, forming oxides only indirectly.
Examples MgCl2(aq) Zn (s)
Zn is alone it wants to take Mg
place. Can it????? Al (s) H2O (g)
18
Work Cited

• Cartoon. Aug. 11, 2006. http//www.nearingzero.n
  et/sbunch3.html
• Activity Series. http//www.pennmanor.net/school
  s/hs/canady/web_page_web_class/taylor_portfolio_we
  bpage/Chemistry/chemistry/reactions/activity_serie
  s.jpg