Slide 1 : Balancing Equations: Chemical and Nuclear
How molecules are symbolized : 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
Balancing equations: MgO : 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
Balance equations by “inspection” : Balance equations by “inspection” Hints: start with elements that occur in one compound on each side. Treat polyatomic ions that repeat as if they were a single entity. 5 2 3 3.5 2 7 4 6 2 2 2 2 6 3 C2H6 + O2 CO2 + H2O a) P4 + O2 P4O10
b) Li + H2O H2 + LiOH
c) Bi(NO3)3 + K2S Bi2S3 + KNO3
d) C2H6 + O2 CO2 + H2O 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
Slide 5 : 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 Balance these skeleton equations:
Slide 6 : 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 NR (no reaction) Zn + Li2CO3 Cu + AlCl3 Returning to reaction types Fe + CuSO4 LiOH + H2 Al2O3 2 Ni + NaCl Al + CuCl2 Li + ZnCO3 Li + H2O Al + O2 3 3 3 2 2 3 2 ½ 2 2 2 3 2 4
Discovery of Radioactivity : 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:
Types of Radioactivity : Types of Radioactivity Types of radiation: 1) a, 2) b, 3)
Alpha () particles are symbolized as 42He
Beta () particles (essentially electrons) are 0–1e
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)
Nuclear equations : Nuclear equations Q. Write the beta decay for C-14 In all cases, charge and mass must be balanced
Practice: pg. 222-3, Q6, Q3 C 14 6 e 0 -1 N 14 7 + Po 209 84 He 4 2 Pb 205 82 + Q. Write the alpha decay for 209Po Q. Complete this fission reaction Kr 94 36
Slide 10 : 6. a) b) c) d) e) a)
b)
c)
d)
e)
Slide 11 : 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 Here are some more to balance:
Some Balanced Equations : Some Balanced Equations 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 For more lessons, visit www.chalkbored.com