Reaction Type Notes

1
Reaction Type Notes
2
Reaction Type Notes

• Most chemical reactions can be categorized into
  one of five types.
• You can usually identify the reaction type by
  looking at the reactants. Once the type of
  reaction is identified, we can predict the
  products

3
Types of Chemical Reactions

• Chemists classify reactions in order to organize
  the many types.

• A synthesis reaction is a reaction in which two
  or more substances react to produce a single
  product.
• General form
• A B ? AB
• or
• A BC ? ABC
• or
• AB CD ? ABCD

4
Types of Chemical Reactions (cont.)

• When two elements react, the reaction is always a
  synthesis reaction.

5
Reaction Type Notes

• Example 2 H2 O2 ? 2 H2O

6
Reaction Type Notes

• Synthesis
• To predict the products for binary compounds,
  put elements together and balance the charges.
  Otherwise, just combine.
• These reactions generally happen spontaneously,
  and are generally exothermic (release energy).

7
Types of Chemical Reactions (cont.)

• In a combustion reaction, oxygen combines with a
  substance and releases energy in the form of heat
  and light.

• Heated hydrogen reacts with oxygen to produce
  heat and water in a combustion reaction. This is
  also a synthesis reaction.

8
Reaction Type Notes

• Hydrocarbon CombustionInvolves a specific case
  of combustion in which a hydrocarbon (a substance
  containing carbon and hydrogen) reacts with
  oxygen to form carbon dioxide and water
• General form
• CxHy O2 ? CO2 H2O

9
Reaction Type Notes

• Example
• 2C2H6 7O2 ? 4CO2 6H2O

10
Reaction Type Notes

• Hydrocarbon Combustion
• To predict products
• At least Carbon Dioxide and water. Always
  exothermic, but often requires a large activation
  energy, leading it to occur spontaneously

11
Reaction Type Notes

• Practice type of reaction and balance
• Al(s) S(s) ? Al2S3
• H2O(l) N2O5(g) ? HNO3(aq)
• NO2(g) O2(g) ? N2O5 (g)

12
Decomposition Reactions

• A decomposition reaction is one in which a single
  compound breaks down into two or more elements or
  new compounds.

• Decomposition reactions often require an energy
  source, such as heat, light, or electricity, to
  occur.
• General form AB ? A B

13
Reaction Type Notes

• Example 2H2O2 ? 2 H2O O2
• (it needs a catalystPotassium Iodide)
• http//www.youtube.com/watch?vOTEX38bQ-2wfeature
  related

14
Reaction Type Notes

• Decomposition
• To predict the products
• Binary compounds separate into their two elements
• You will be given a handout to predict others
• Generally not spontaneous, and generally
  endothermic

15
Reaction Type Notes

• Practice type of reaction and balance
• 4. Al2O3(s) ? Al(s) O2(g)
• 5. Ni(OH)2(s) ? NiO(s) H2O(l)
• 6. NaHCO3(s) ? Na2CO3(aq) CO2(g) H2O(l)

16
Replacement Reactions

• A reaction in which the atoms of one element
  replace the atoms of another element in a
  compound is called a single replacement reaction.
• A BX ? AX B

17
Replacement Reactions (cont.)

• A metal will not always replace a metal in a
  compound dissolved in water because of differing
  reactivities.

• An activity series can be used to predict if
  reactions will occur.

18
Replacement Reactions (cont.)

• Halogens frequently replace other halogens in
  replacement reactions.

• Halogens also have different reactivities and do
  not always replace each other.

19
Reaction Type Notes

• Example 2 Na 2 H(OH) ? 2 Na(OH) H2

20
Reaction Type Notes

• Single displacement
• To predict the products The element switches
  places with the element of similar charge within
  the compound.
• If the element is more reactive then the one it
  attempts to replace, then the reaction will be
  spontaneous and exothermic. Otherwise, it will
  not be spontaneous and will be endothermic
  (require the input of energy).

21
Reaction Types

• Activity Series
• Most Active Cations ? Least Active
• Lithium
• Rubidium
• Potassium
• Barium
• Calcium
• Sodium
• Hydrogen (in water)
• Magnesium
• Aluminum
• Manganese

• Zinc
• Chromium
• Iron
• Nickel
• Tin
• Lead
• Hydrogen (in acids)
• Copper
• Mercury
• Silver
• Platinum
• Gold
• Red not included in book values

22
Reaction Type Notes

• Activity Series
• Most Active Anions ? Least Active
• Fluorine
• Oxygen
• Chlorine
• Nitrogen
• Bromine
• Iodine

• Sulfur
• Selenium
• Astatine
• Phosphorus
• Tellurium
• Arsenic
• Polonium
• Red not included in book values

23
Reaction Type Notes

• Practice
• Type of reaction/ will it react and balance
• 7. K(s) ZnCl2(aq) ? Zn(s) KCl(aq)
• 8. Al(s) Pb(NO3)2(s) ? Pb(s) Al(NO3)3(aq)

24
Replacement Reactions (cont.)

• Double replacement reactions occur when ions
  exchange between two compounds.

• This figure shows a generic double replacement
  equation.

25
Reaction Type Notes

• Double displacement
• To predict the products
• Like charged particles switch places
• Both compounds are initially stable and so
  reactions will usually not be spontaneous as
  solids. If compounds can be dissolved and
  dissociated (broken apart) then reaction will
  usually occur spontaneously to some degree, but
  not be highly exothermic

26
Replacement Reactions (cont.)

• This table shows the steps to write double
  replacement reactions.

27
Replacement Reactions (cont.)

• A solid product produced during a chemical
  reaction in a solution is called a precipitate.

• All double replacement reactions produce either
  water, a precipitate, or a gas.

28

• Example 2 NaI(aq) Pb(NO3)2(aq) ?PbI2(s)
  2NaNO3(aq)

29
Reaction Type Notes

• Practice type of reaction and balance
• 9. LiI(aq) AgNO3(aq) ? AgI(s) LiNO3(aq)
• 10. BaCl2(aq) K2CO3(aq) ? BaCO3(s) KCl(aq)
• 11. Na2C2O4(aq) Pb(NO3)2(aq) ? PbC2O4(s)
  NaNO3(aq)

30
Reaction Type Notes

• Most reactions which do not appear to fit any of
  these five patterns are usually a combination of
  two or more of them happening simultaneously

31
Replacement Reactions (cont.)

• This table summarizes different ways to predict
  the products of a chemical reaction.

32
(No Transcript)