Illustrated Guide to Home Chemistry Experiments

302 DIY Science: Illustrated Guide to Home Chemistry Experiments

SBSTITUTIU oNS ANd modIfICATIoNS

• You may substitute any containers of similar size for the 150 mL beakers.


• You may substitute a commercially made salt bridge for the plastic tubing and cotton ball.


• You may substitute an aluminum or zinc electrode for the magnesium electrode. If you do that, replace the 1.0 M
  magnesium sulfate solution with 1.0 M aluminum sulfate or 1.0 M zinc sulfate, respectively.


• If you do not have a bench solution of 1 M sodium chloride, you can make it up by weighing 5.84 g of sodium chloride
  and dissolving it in sufficient water to make up 100 mL of solution. You may substitute table salt for the sodium chloride.
  Concentration is not critical.


• If you do not have a bench solution of 1.0 M magnesium sulfate, you can make it up by weighing 6.02 g of anhydrous
  magnesium sulfate or 12.32 g of magnesium sulfate heptahydrate and dissolving it in sufficient water to make up 50 mL of
  solution. You may substitute Epsom salts for the magnesium sulfate heptahydrate. Concentration is not critical.


• If you do not have a bench solution of 1.0 M copper sulfate, you can make it up by weighing 7.98 g of anhydrous copper
  sulfate or 12.49 g of copper sulfate pentahydrate and dissolving it in sufficient water to make up 50 mL of solution.
  Concentration is not critical.

POCEDURER
1.ou have not already done so, put on your splash If y
goggles, gloves, and protective clothing.

2. Transfer 50 mL of 1.0 M magnesium sulfate solution to
   one beaker, and 50 mL of 1.0 M copper sulfate solution to
   the other beaker.


3. Use steel wool or sandpaper to polish each of the
   electrodes to remove surface oxidation, oils, and other
   contaminants.


4. Clip one end of each patch cable to an electrode and the
   other ends of the patch cables to the DMM terminals.


5. Immerse the magnesium electrode in the beaker of
   magnesium sulfate solution, and the copper electrode in
   the beaker of copper sulfate solution.


6. Observe the voltage reading on the DMM. No voltage is
   detected, because no circuit yet exists.


7. Plug one end of the plastic tubing tightly with cotton. Use
   the Beral pipette to fill the plastic tubing with 1 M sodium
   chloride solution, making sure that there are no air bubbles
   in the tubing. (If the solution runs out of the plugged end
   as you fill the tubing, the plug isn’t tight enough.) When the
   tubing is full, plug the open end tightly with cotton and add
   a few more drops of sodium chloride solution to make sure
   that the plug is saturated with solution.
   8. Check again to make sure that there are no air bubbles in
   the tubing, and then immerse one end of the tubing in the
   beaker of magnesium sulfate solution and the other end
   in the beaker of copper sulfate solution.
   9. Record the voltage and current readings on the DMM on
   line A of Table 16-6.
   Add 50 mL of water to the beaker of magnesium sulfate,
   stir to mix thoroughly, and record the voltage and current
   readings on the DMM on line B of Table 16-6.
   Add 50 mL of water to the beaker of copper sulfate, stir
   to mix thoroughly, and record the voltage and current
   readings on the DMM on line C of Table 16-6.

dISpoSAL: The magnesium sulfate solution can be

flushed down the drain with copious water. precipitate

the copper ions by adding sodium carbonate solution

and filtering the solid copper carbonate precipitate,

which may be disposed of with household waste; the

supernatant fluid may be flushed down the drain. The

electrodes can be retained for later use.

FIGURE 16-4: A voltaic cell made up of two half-cells

10.

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