Name:
Period:
Chemistry
Precipitation Lab
Introduction: Precipitation is the formation of a solid in a solution and its reactions can be used for making pigments and
removing salts and other harmful solids from water at treatment facilities. For example, if a precipitate test indicates the
presence of lead within water, authorities can take appropriate precautions to keep the public safe. Today, we are combining
clear solutions of different compounds to observe if any insoluble products (precipitates) are formed. Indicators of
precipitation are:
color changes within a solution
a solution becoming cloudy and opaque
the appearance of small solids or crystals.
Precipitation involves a double replacement reaction in the general form:
AX (aq) + BY (aq) -> AY (aq) + BX (solid)
Procedure: In small lab groups:
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Obtain a clear transparency grid for the reactions. Some boxes are crossed out to prevent duplicate reactions
Eleven dropper bottles containing the proper solutions can be found near the middle lab stations. Groups will have to
cooperate and share the dropper bottles; organize the dropper bottles once you’re finished.
You only need one drop of each compound in the grid. Here’s a helpful strategy: grab a solution and place one drop in
every column. Once the grids are filled, get the appropriate solutions and add one drop to each row. Be sure to let the
drops fall through space- you don’t want the tip of the dropper to rub against the transparency, otherwise you will get
contaminated results
Get a colored pencil, bubble in a small circle for any precipitation that you observe on the reaction grid provided.
Analysis I:
Name the eleven solutions below:
1. KBr
______________________________________
2. MgCl2
______________________________________
3. AgNO3
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4. Ca(NO3)2
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5. Na2CO3
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6. (NH4)2SO4
______________________________________
7. BaCl2
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8. NaC2H3O2
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9. Pb(NO3)2
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10. NaOH
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11. Al(NO3)3
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Analysis II: In the lab today, you should have observed roughly 20 precipitation reactions, all indicated by color changes,
appearance of crystals, or cloudy solutions. Out of those 20, pick/choose 10 and write the chemical reaction. Start with the
reactants and predict the products & using the solubility guidelines on p. 920, indicate the precipitate that was formed using
(s). Remember, double displacement reactions form precipitates, so indicate the product which was the precipitate. Write out
the Equation. Below it write the Ionic Equation with Spectator Ions circled, and below that write the Net Ionic Equation
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