Reactions Involving Ions: Molecular vs. Ionic Equations

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Reactions Involving IonsMolecular vs. Ionic
Equations

• Chemical Reaction can be expressed by
• Molecular Equation (balanced chemical equation)
• Complete Ionic Equation (showing all ions in
  reaction)
• Net Ionic Equation (showing only those ions
  directly involved in reaction)
• Consider
• Copper (III) sulfate reacts with sodium hydroxide
  to form copper (III) hydroxide and sodium sulfate
  (all in water).

• Express reaction in molecular, complete ionic,
• and net ionic equations

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8 Simple Rules For Common Ionic Compounds
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Song For Solubility!!
(Taken from Cornell University Adapted by Daley
Sing to Rhythm of 99 Bottles) 
Potassium, sodium, and ammonium salts, 
Whatever they may be, Can always be depended
on For solubility.  Asked about the nitrates
or acetates The answer is always clear, They
each and all are soluble, Is all we want to
hear.  Most every chloride's soluble At least
we've always read Save silver, mercurous
mercury And (slightly) chloride of lead. Take
the Bromide and iodide salts There soluble as
can be Save silver, mercury, and lead That
precipitate as you see Every single sulfate Is
soluble ,  'Tis said 'Cept barium and
strontium And calcium and lead. 
Hydroxides of metals won't dissolve That is, all
but three Potassium, sodium and
ammonium Dissolve quite readily. And then you
must remember That you must not
"forgit" Calcium, barium, strontium Dissolve a
little bit.  The carbonates are insoluble, 
It's lucky that it's so, Or else, our marble
buildings Would melt away like snow.  (Repeat
with feeling)  Only note is that all Lithium
salts are Soluble too!!!
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Predicting Whether a Precipitation Reaction
Occurs Writing Equations
a) Calcium Nitrate and Sodium Sulfate solutions
are added together.
Molecular Equation
Ca(NO3)2 (aq) Na2SO4 (aq)
CaSO4 (s) NaNO3 (aq)
Total Ionic Equation
Ca2(aq)2 NO3-(aq) 2 Na(aq) SO4-2(aq)
CaSO4 (s) 2 Na(aq) 2 NO3-(aq)
Net Ionic Equation
Ca2(aq) SO-4(aq)
CaSO4 (s)
Spectator Ions are Na and NO3-
b) Ammonium Sulfate and Magnesium Chloride are
added together.
In exchanging ions, no precipitates will be
formed, so there will be no chemical reactions
occurring! All ions are spectator ions!
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Precipitation Reactions Will a Precipitate Form?
If we add a solution containing potassium
chloride to a solution containing ammonium
nitrate, will we get a precipitate?
KCl(aq) NH4NO3 (aq) K(aq)
Cl-(aq) NH4(aq) NO3-(aq)
By exchanging cations and anions we see that we
could have potassium chloride and ammonium
nitrate, or potassium nitrate and
ammonium chloride. In looking at the solubility
table it shows all possible products as soluble,
so there is no net reaction!
KCl(aq) NH4NO3 (aq) No Reaction!
If we mix a solution of sodium sulfate with a
solution of barium nitrate, will we get a
precipitate? From the solubility table it shows
that barium sulfate is insoluble, therefore we
will get a precipitate!
Na2SO4 (aq) Ba(NO3)2 (aq)
BaSO4 (s) 2 NaNO3 (aq)
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Figure 4.6 Reaction of magnesium chloride and
silver nitrate. Photo courtesy of American Color.
Write molecular and ionic equations for this
reaction.
Ionic equation Ag(aq) Cl-(aq) ?AgCl(s)
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Oxidation-Reduction
2Na (s) Cl2(g)? 2NaCl(s)
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Acid-Base
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Definition of Acid Base

• Arrhenius
• Acid substance that produces H ions
• Base substance that produces HO- ions
• Bronsted Lowry
• Acid substance that donates a proton to another
  substances
• Base substance that accepts a proton to another
  substances

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Acids - A Group of Covalent Molecules Which Lose
Hydrogen Ions to Water Molecules in
Solution
When gaseous hydrogen iodide dissolves in water,
the attraction of the oxygen atom of the water
molecule for the hydrogen atom in HI is greater
that the attraction of the of the iodide ion for
the hydrogen atom, and it is lost to the water
molecule to form an hydronium ion and an iodide
ion in solution. We can write the hydrogen atom
in solution as either H(aq) or as H3O(aq) they
mean the same thing in solution. The presence of
a hydrogen atom that is easily lost in solution
is an Acid and is called an acidic solution.
The water (H2O) could also be written above the
arrow indicating that the solvent was water in
which the HI was dissolved.
HI(g) H2O(L) H(aq) I
-(aq)
HI(g) H2O(L) H3O(aq) I
-(aq)
H2O
HI(g) H(aq) I
-(aq)
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Figure 4.8B Red cabbage juice added to solutions
in the beakers.Photo courtesy of James Scherer.
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Molecular representation of ammonium hydroxide.
NH3(aq) H2O(l) ? NH4(aq) OH-(aq)
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Reaction of nitric acid with water.
HNO3(aq) H2O(l) ? NO3-(aq) H3O(aq)
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Beaker with Na(aq), C2H302-(aq), and SrS04
(solid).
Na2SO4 (aq) Sr(C2H3O2)2(aq) ? SrSO4 (s)
NaC2H3O2 (aq)
2 Na(aq) SO4-2 (aq) Sr2(aq) 2C2H3O2
-(aq) ? SrSO4 (s) 2 Na(aq) 2C2H3O2 -(aq)
SO4-2 (aq) Sr2(aq)? SrSO4 (s)
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Figure 4.9 Reaction of a carbonate with an
acid.Photo courtesy of American Color.
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Figure 4.10 Iron nail and copper ( II)
sulfate.Photo courtesy of American Color.
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Figure 4.10 Fe reacts with Cu2(aq) and
makesCu(s).Photo courtesy of American Color.
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Figure 4.10 The copper metal plates out on the
nail.Photo courtesy of American Color.
Write a net ionic equation for this reaction!
Cu2(aq) Fe(s) ? Cu(s) Fe2(aq)
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Percent Yield/Limiting Reactant Problem - II
N2 (g) 3 H2 (g)
2 NH3 (g)
Solution Cont.
We have 3.066 moles of Nitrogen, and it is
limiting, therefore the theoretical yield of
ammonia is
2 mol NH3 1 mol N2
3.066 mol N2 x
6.132 mol NH3

(Theoretical Yield) 6.132 mol NH3 x
104.427 g NH3

(Theoretical Yield)
17.03 g NH3 1 mol NH3
Actual Yield Theoretical Yield
Percent Yield x
100
98.67 g NH3 104.427 g NH3
Percent Yield
x 100 94.49
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Molarity (Concentration of Solutions) M
Moles of Solute Moles Liters of
Solution L
M
solute material dissolved into the solvent In
air , Nitrogen is the solvent and oxygen, carbon
dioxide, etc.

are the solutes. In sea water , Water is the
solvent, and salt, magnesium chloride, etc.

are the solutes. In
brass , Copper is the solvent (90), and Zinc is
the solute(10)
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Fig. 3.11
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Preparing a Solution - I

• Prepare a solution of Sodium Phosphate by
  dissolving 3.95g of Sodium Phosphate into water
  and diluting it to 300.0 ml or 0.300 l !
• What is the Molarity of the salt and each of the
  ions?
• Na3PO4 (s) H2O(solvent) 3 Na(aq)
  PO4-3(aq)

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Figure 4.22C Titration of an unknown amount of
HCl with NaOH (3). Photo courtesy of American
Color.
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