Transcript Slide 1

Net Ionic Equations
Precipitates
► A precipitate is the solid substance that
separates from solution
► Precipitates can also form from
reactions
► Reactions that produce a precipitate are
called precipitation reactions
► Most ionic compounds dissolve in water
► Solutes that produce ions in solution are
called electrolytes because their
solutions can conduct electricity
Electrolytes:
An ionic compounds dissociates as it
dissolves in water Ions separate from the solid
and become hydrated or
surrounded by water
molecules.
The ions move freely and the
solution is able to conduct
electricity.
Ionic compounds that dissociate completely
are strong electrolytes
Nonelectrolytes:
► Most solutions of molecular compounds
do not conduct electricity and are called
nonelectrolytes
The molecules of a
nonelectrolyte separate
but stay intact. The
solution is nonconducting
because no ions are
generated.
Some ionic compounds have low solubilities in
water but are still strong electrolytes because what
does dissolve is 100% dissociated.
Electrolytes:
► The dissociation of ionic compounds
may be described with chemical
equations

Na 2SO 4 ( s )  2 Na (aq)  SO (aq)
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► The
hydrated ions, with the symbol
(aq), have been written separately
► Since physical states are often omitted,
you might encounter the equation as:

Na 2SO 4  2 Na  SO
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Know your Solubility Rules!
► Ionic compounds often react when their
When a
aqueous solutions combine
solution of
Pb(NO3)2 is
mixed with
a solution of
KI the
yellow
precipitate
PbI2 rapidly
forms.
Know your Solubility Rules!
►A
precipitation reaction may be represented
with a molecular, ionic, or net ionic
equation:
Molecular: Pb(NO3 ) 2 (aq)  2KI(aq)  PbI 2 ( s )  2KNO3 (aq )
Ionic:
Pb 2 (aq )  2NO3- (aq )  2K  (aq )  2I - (aq ) 
Net Ionic:
► The
PbI2( s )  2K  (aq )  2NO3- (aq )
Pb 2 (aq )  2I  (aq )  PbI 2 ( s )
most compact notation is the net ionic
equation which eliminates all the non-reacting
spectator ions from the equation
Types of chemical equations
► Here
is a typical molecular equation:
Cd(NO3)2(aq) + Na2S(aq)  CdS(s) + 2NaNO3(aq)
► We
can write this as an ionic equation (all
compounds that are (aq) are written as ions):
Cd2+(aq) + 2NO3–(aq) + 2Na+(aq) + S2–(aq)
 CdS(s) + 2Na+(aq) + 2NO3–(aq)
► To
get the NET ionic equation we cancel out
all terms that appear on both sides:
Net:
Cd2+(aq) + S2–(aq)  CdS(s)
Ag+ + Cl-  AgCl (s)
Criteria for balanced net ionic equations:
1) Material balance – the same number of
each type of atom on each side of the
arrow
2) Electrical balance – the net electrical
charge on the left side of the arrow must
equal the net electrical charge on the
right side of the arrow
Remember that the charge on an ion must be included when it is
not in a compound. Adding the charges on all the ions on one
side of the arrow gives the net electrical charge.
First write the skeleton equation
2 NaOH(aq) + MgCl2(aq)
 Mg(OH)2(s) + 2 NaCl(aq)
Next, balance the equation
Second write the Ionic equation:
2Na+(aq) + 2OH-(aq) + Mg2+(aq) + 2Cl-(aq)
 Mg(OH)2(s) + 2Na+(aq) + 2Cl-(aq)
Third cancel the spectator ions and write the
Net ionic equation:
2OH-(aq) + Mg2+(aq)  Mg(OH)2(s)
Practice Equations
Write balanced net ionic equations:
1)
CuSO4(aq) + BaCl2(aq) 
1)
Fe(NO3)3(aq) + LiOH(aq) 
2)
Na3PO4(aq) + CaCl2(aq) 
3)
Na2S(aq) + AgC2H3O2(aq) 
Net Ionic Equation Solutions
Net: SO42–(aq) + Ba2+(aq)  BaSO4(s)
Net: Fe3+(aq) + 3OH–(aq)  Fe(OH)3(s)
Net: 2PO43–(aq) + 3Ca2+(aq)  Ca3(PO4)2(s)
Net: S2–(aq) + 2Ag+(aq)  Ag2S(s)