PowerPoint - Balancing Equations - Chemical and Nuclear

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Balancing Equations
Chemical and Nuclear
2
How molecules are symbolized

• Cl2 2Cl 2Cl2

• Molecules may also have brackets to indicate
  numbers of atoms. E.g. Ca(OH)2

• Notice that the OH is a group
• The 2 refers to both H and O
• How many of each atom are in the following?
• a) NaOH
• b) Ca(OH)2
• c) 3Ca(OH)2

Na 1, O 1, H 1
Ca 1, O 2, H 2
Ca 3, O 6, H 6
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Balancing equations MgO

• The law of conservation of mass states that
  matter can neither be created or destroyed
• Thus, atoms are neither created or destroyed,
  only rearranged in a chemical reaction
• Thus, the number of a particular atom is the same
  on both sides of a chemical equation
• Example Magnesium Oxygen (from lab)
• Mg O2 ? MgO

• However, this is not balanced
• Left Mg 1, O 2
• Right Mg 1, O 1

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Balance equations by inspection
From Mg O2 ? MgO 2Mg O2 ? 2MgO
is correct Mg ½O2 ? MgO is
incorrect Mg2 O2 ? 2MgO is
incorrect 4Mg 2 O2 ? 4MgO is incorrect

• Hints start with elements that occur in one
  compound on each side. Treat polyatomic ions
  that repeat as if they were a single entity.

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a) P4 O2 ? P4O10 b) Li H2O ? H2
LiOH c) Bi(NO3)3 K2S ? Bi2S3
KNO3 d) C2H6 O2 ? CO2 H2O
2
2
2
2
6
3
2
3
3.5
C2H6 O2 ? CO2 H2O
2
7
4
6
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Balance these skeleton equations

• a) Mg 2HCl ? MgCl2 H2
• b) 3Ca N2 ? Ca3N2
• c) NH4NO3 ? N2O 2H2O
• d) 2BiCl3 3H2S ? Bi2S3 6HCl
• e) 2C4H10 13O2 ? 8CO2 10H2O
• f) 6O2 C6H12O6 ? 6CO2 6H2O
• g) 3NO2 H2O ? 2HNO3 NO
• h) Cr2(SO4)3 6NaOH ? 2Cr(OH)3 3Na2SO4
• i) Al4C3 12H2O ? 3CH4 4Al(OH)3

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Returning to reaction types
K
Na
Li
Ca
Mg
Al
Zn
Fe
Ni
Sn
Pb
H
Cu
Hg
Ag
Au

• We have looked at several types of reactions
  without worrying about balancing
• However, all equations should be balanced
• Predict the products and balance these
• (recall, metals above replace metals below,
  reactions with water yield metal hydroxides)

Cu Fe2(SO4)3
2
3
3
Fe CuSO4 ?
NR (no reaction)
Ni NaCl ?
3
2
2
3
Cu AlCl3
Al CuCl2 ?
Zn Li2CO3
Li ZnCO3 ?
2
LiOH H2
Li H2O ?
½
2
2
2
Al2O3
Al O2 ?
3
2
4
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Discovery of Radioactivity

• Radioactivity is the release of energy or
  particles when an atom disintegrates (demo)
• Radioactivity was discovered when minerals were
  exposed to film through an opaque cover
• The 3 types of radioactivity can be shown by
  passing emissions through an electrical field

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Types of Radioactivity

• Types of radiation 1) a, 2) b, 3) ?
• Alpha (?) particles are symbolized as 42He
• Beta (?) particles (essentially electrons) are
  01e
• Gamma (g) rays are symbolized as 00?
• You can determine the composition of each a
  mass of 4 u, charge of 2 (2 p, 2 n0, 0 e)
• Other symbols proton 11p, neutron 10n
• There are different terms to describe the
  different types of nuclear reactions
• alpha decay means an a particle is given off.
• Other beta decay, fusion (meaning to bring
  together), fission (meaning to break apart)

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Nuclear equations

• Q. Write the beta decay for C-14

14
0
14
?

C
e
N
6
7
-1
Q. Write the alpha decay for 209Po
209
4
205
?

Po
He
Pb
84
2
82
Q. Complete this fission reaction
94
Kr
36

• In all cases, charge and mass must be balanced
• Practice pg. 222-3, Q6, Q3

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• 6. a) b) c) d)
  e)

• a)
• b)
• c)
• d)
• e)

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Here are some more to balance

• a) 2KNO3 ? 2KNO2 O2
• b) 2Pb(NO3)2 ? 2PbO 4NO2 O2
• c) P4 6I2 ? 4PI3
• d) 3MgO 2H3PO4 ? Mg3(PO4)2 3H2O
• e) Br2 2KI ? I2 2KBr
• f) Ca(OH)2 2HNO3 ? Ca(NO3)2 2H2O
• g) Bi2O3 3H2 ? 2Bi 3H2O
• h) 3Fe 2O2 ? Fe3O4
• i) 2CaO 5C ? 2CaC2 CO2

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Question 3 pg. 252

• a) 2Li 2H2O H2 2LiOH
• b) P4 5O2 P4O10
• c) 2C2H6 7O2 4CO2 6H2O
• d) CS2 3O2 CO2 2SO2
• e) 2AsCl3 3H2S As2S3 6HCl
• f) 3AgNO3 FeCl3 3AgCl Fe(NO3)3
• g) 2KClO3 2KCl 3O2
• h) 2SO2 O2 2SO3

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