Solubility of Metal Salts

Materials

Test tube rack

Multi-well titer plates (24 or 36 well)

Hot water bath set at 60C, in the hood

Dropper bottles of 0.1M metal nitrate solutions:

Al⁺³, Fe⁺³, Pb⁺², Ba⁺², Zn⁺², Cu⁺², Co⁺², K⁺¹

Dropper bottles containing 2M solutions of anions:

Na₂S, Na₂CO₃, Na₂SO₄, NaSCN

Dropper bottle containing 3M NaOH

Dropper bottle containing coded unknown sample

1. 
   It is suggested that this portion of the experiment be done in the hood to minimize the unpleasant odor in the room from the hydrogen sulfide gas.
   
2. 
   A hot water bath has been set up in the hood for your use. There is room for 3 or 4 groups to heat samples.
   
3. 
   Obtain 9 small clean test tubes and add 10 drops of the 0.1 M metal nitrate solutions into separate tubes with the appropriate label. The metal cations available should be Al³⁺, Fe³⁺, Pb²⁺, Ba²⁺, Zn²⁺, Cu²⁺, Co²⁺, K⁺, and your unknown.
   
4. 
   Add 4 drops of 1 M sodium sulfide to each tube. Mix. Place the tubes in the hot water bath and heat for ten minutes. Record your observations. In the column labeled “Formula” write the chemical formula of the precipitate formed (write “complex” if a complex forms or leave blank for no reaction). For two representative precipitates formed, write a chemical equation (molecular, not net ionic or complete ionic) for the reaction.
   
5. 
   Empty the tubes into the waste containers provided, and dispose of them as instructed.