4. What is the classification of the reactions in this lab?
Double Replacement
Compare the reactions of hydrochloric acid with lead II nitrate copper II sulfate.
The reaction of hydrochloric acid and lead II nitrate formed a
precipitate and the reaction of hydrochloric acid and copper II
sulfate had a color change and did not form a precipitate.
3.
Sodium chloride and lead nitrate had no color change and formed
a white precipitate. Sodium chloride and copper II sulfate had a
color change and no precipitate.
Compare the reactions of sodium chloride with lead II nitrate
and copper sulfate.
AB + CD —> AD + CB
The general formula for a double replacement is:
Chemical reactions involve the rearrangement of elements to form new compounds. According to the law
of conservation of matter, the products must have the
same number of atoms as the reactants. Double replacement reactions occur when the positive ion of
one compound displaces the positive ion of another
compound. So, the reaction has two compounds on the
reactant side and two on the product side. This swap
of chemical bonding partners produces two new compounds that are different from the reactants at the start.
Usually in double replacement reactions, a precipitate
forms. A precipitate is a solid that separates out of a
solution.
Name____________________________________
Double Replacement Reaction
Compare the reactions of KI with lead II nitrate and copper
II sulfate.
Student
Directions:
Six lab stations will be set up around the room. Each stations will have the pair of
reagents indicated on the chart to the right. We will start four students at each
station. The teacher will announce when it is time to move to the next station.
Write the name for each compound in the data table under its formula.
4.
Write the balanced equation in the space provided. If you are not finished
when it is time to move, you can balance your equation at the end of lab.
3.
Record your observations as indicated on the data table to the right.
2.
At each station, add three drops of each reactant in a clean well in the well
plate.
1.
Teacher Preparation:
1. Make the following solutions:
2molar KI
1 molar Pb(NO3)2
1 molar CuSO4
2 molar NaCl
3 molar HCl
2. Set up 6 stations, one for each reaction. Each reagent should
be in a beaker with a dropper pipette.
2.
Potassium iodide and lead nitrate showed a color change and a
precipitate. Potassium iodide and copper II sulfate changed from
blue to colorless and had no precipitate.
1.
React the first column with the second column.
Reactant 1
2KI
+
Reactant 2 Record observations and write a
balanced equation in the space
below.
Pb(NO3 )2
→
+ Pb(NO3)2
2NaCl
+ CuSO4
→
2KI
2KI + Pb(NO3)2 —> 2KNO3 + PbI2
PbI2 is a yellow insoluble solid seen as
a precipitate
KNO3 is a colorless soluble salt
CuSO4 + 2KI—> CuI2 + K2SO4
K2SO4 is white and soluble
CuI2 is white and soluble
No precipitate is visible
→
NaNO3 is very soluble and colorless
PbCl2 is poorly soluble and shows
up as a white precipitate
2HCl + Pb(NO3 )2 —> PbCl2 + 2HNO3
+ Pb(NO3 )2
→
2HCl
2NaCl + CuSO4→ Na2SO4 + CuCl2
Na2SO4 is soluble and colorless
CuCl2 is soluble and blue green
No precipitate is visible
+ CuSO4 →
2NaCl
3. Depending on the level of your students, you can have lower
level students omit #3.
PbCl2 iis insoluble and shows up
as a white precipitate
HNO3 is soluble and colorless
+ CuSO4 → 2HCl + CuSO4 —> CuCl2 + H2SO4
CuCl2 is soluble and blue green
No precipitate is visible
2HCl