Chemistry 2013
Precipitates and Net Ionic Equations Lab
Name _________________
For each compound, write the two ions that make it up. (Ex: K2CrO4 = K+ CrO42- )
In each square, write the two new compounds that will form.
Cross out any compounds that you KNOW will be soluble in water and therefore will NOT be precipitates.
*We won’t be using any chromates (CrO4) in class because they are toxic. I’ll provide data for these plus the (NH4)2SO4 reactions.
* K2CrO4
CuSO4
Ba(OH)2
Pb(NO3)2
Na2CO3
KI
1.
2.
3.
K+ CrO42-
AgNO3
(NH4)2SO4
KI
Ag + NO3-
Ag2CrO4
KNO3
NH4CrO4
KNO3
K2CrO4
KI
Na2CO3
Na2CrO4
K2CO3
Pb(NO3)2
PbCrO4
KNO3
Ba(OH)2
BaCrO4
KOH
CuSO4
CuCrO4
K2SO4
O’Ryan
(NH4)2SO4
Chemistry 2013
Precipitates and Net Ionic Equations Lab
Procedure
1.
Using a reaction surface, place a couple drops of each pair of ionic compounds in a well.
2.
Record your observations for each combination including the color and whether or not a precipitate is formed.
Precipitate may be abbreviated as PPT. Precipitate and its color (e.g. WHITE PPT).
If no reaction occurs (the mixed drop remain clear) write N.R. for no reaction or draw a dash .
3.
Be sure to look at the reactions with both a white (paper) and black (lab table) background.
Data
K2CrO4
AgNO3
(NH4)2SO4
KI
Na2CO3
Pb(NO3)2
Ba(OH)2
CuSO4
O’Ryan
red-brown PPT
CuSO4
Ba(OH)2
Pb(NO3)2
Na2CO3
KI
(NH4)2SO4
Chemistry 2013
Background:
A chemical reaction is a chemical change where substances change into new substances. A chemical equation is a shorthand
notation that describes the reaction. The substances on the left side of the arrow are the reactants and the substances on the right
side are the products. The arrow means "yields" or "reacts to produce." reactants products
The substances can be solid, liquid, gaseous, or aqueous (dissolved in water) and are shown as subscripts in parentheses. Often,
the phases of elements will change during the reaction.
• (g) gas
• (l) liquid
• (s) solid
• (aq) aqueous–dissolved in water
Spectator Ions: Ions that don’t participate in a reaction (they show up on both sides of the equation).
Net Ionic Equation: Total ionic equation with the spectator ions removed.
Conclusion:
Write complete ionic equations and then net ionic equations for the following reactions. The net ionic equation will show the
compound that produced a precipitate on the right. Be sure to include (s) after the compound to indicate that it is a solid.
Example:
Reaction: 2 AgNO3 (aq) + K2CrO4 (aq) → Ag2CrO4 (s) + 2 KNO3 (aq)
Spectator Ions
K+ and NO3-
Complete Ionic Equation: 2Ag+ (aq) + 2NO3 – (aq) + 2K+ (aq) + CrO4 -2(aq) Ag2CrO4 (s) +2 K+(aq) +2NO3 – (aq)
Net Ionic Equation: 2Ag+ (aq) + CrO4 -2(aq)  Ag2CrO4 (s)
Only shows ions that
formed precipitate
1. What does aqueous mean?
2. Name 2 polyatomics that tend to form insoluble compounds. (In a reaction, these would form precipitates.)
3. Write complete and net ionic equations for 4 of the reactions in this lab. Remember to choose reactions that formed
precipitates.
O’Ryan
Chemistry 2013
O’Ryan