Chemistry 130 Laboratory

AB + CD  à AD + BC 

In the reactions you will study, each of the compounds will form ions in solution, then the ions will recombine to form new compounds, or remain in solution. In today's experiment you win perform the reaction, observe the results, then test known compounds and design further experiments using these known compounds to test your hypotheses about what has occurred. If you see no visible signs of reaction, such as a temperature change, a precipitate being formed, or a gas being released, it may be that the compounds have simply dissolved in solution without recombining. If you feel this is the case, simply write "no reaction", however you must justify this conclusion. 

An example of a double displacement reaction is the following: 

NaCl + AgNO₃   à NaNO₃ + AgCl

When solutions of the two reactants are combined, a white precipitate is formed. This is definite evidence that a reaction has occurred. In this reaction, sodium chloride dissolves in solution to form sodium ions Na+ and chloride ions (Cl-) Silver nitrate dissolves to give silver ions (Ag+) plus nitrate ions (NO3- ). These ions recombine to form the products as shown in the reaction. How can you tell which product or if both are the white precipitate? One way would be to take a small amount of sodium nitrate (NaNO3) and see if it dissolves in water. If it does, you can rule it out as the product that precipitated. Likewise you could see if silver chloride dissolves in water. If you did these experiments you would find that NaNO3 does indeed dissolve in water whereas AgCl does not. You would conclude that the white precipitate formed was AgCl.  
 

NaOH + HCl     à     NaCl + H₂0 

The only evidence of a reaction having occurred is a temperature change. The reaction vessel feels warm to the touch. This heat is released when water forms from the hydroxide ion (OH-) and the proton (H+).

In today's experiment you will combine reactants, notice any evidence of a reaction (precipitate, color change, temperature change, etc.) and determine what reaction has occurred, if any, by observing other combinations of reagents and testing known compounds from the laboratory.

1. Take a test tube of the size you will be using in today's experiment and add to it 3 mL of water. Use this as a calibration device.
2. Mark the other test tubes you will be using to this mark. Now add another 3 mL of water to the first tube. Again mark the tubes you will be using so that each now will have a mark representing 3 mL and 6 mL.
3. Add each solution in 3 mL quantities.
4. Use a clean test tube for each experiment.
5. Make a table in your lab notebook having a column for the reaction which has occurred (or "no reaction), and a column for your observations and further experiments or evidence for your conclusions (leave substantial space for each entry).