Ben

Plan: Preform successful electrolysis of Zinc chloride and obtain Zinc. Why-To see how electrolysis works. Also to see if I could obtain a metallic product that conducts electricity. The method is similar to the below instructions.

The following information is from http://www.practicalchemistry.org/experiments/electrolysis-of-zinc-chloride,50,EX.html Another resource: http://www.rsc.org/education/teachers/learnnet/videodemos/electrolysiszinc.pdf Related Images:

Apparatus and chemicals
Eye protection Fume cupboard Low voltage (0-12 V) powerpack and electrical leads Graphite electrodes, 2, supported in an electrode holder or bung Ammeter and/or bulb (in holder) Circuit tester (optional) Bunsen burner, tripod and heat resistant mat Pipeclay triangle Crucible Clamp and stand Metal spatula Tongs Plastic beaker Filter paper and funnel Indicator paper and/or starch-iodide paper Solid zinc chloride (**Corrosive**, **Danger to the environment**) Distilled water

Technical notes
Zinc chloride (**Corrosive, Dangerous for the environment**) Refer to CLEAPSS Hazcard 108 (2007: 108A). Chlorine (**Toxic, Dangerous for the environment**) Refer to CLEAPSS Hazcard 22 See diagram below.

Procedure
HEALTH & SAFETY: Work in a fume cupboard. Wear eye protection.
 * Setting up the electrolysis**
 * a** Set up a heat-resistant mat, tripod, Bunsen burner and pipeclay triangle. Put the crucible onto the pipeclay triangle, ensuring that it is sitting firmly and is in no danger of falling through.
 * b** Set up the electric circuit with the power pack, ammeter and/or bulb and electrodes in series. Short the circuit at the electrodes with a key or the metal spatula.
 * c** Clamp the electrodes so that they almost touch the bottom of the crucible but do not touch each other.
 * d** Fill the crucible to within about 5 mm of the top with the powdered zinc chloride. As it melts the solid will shrink in volume as air escapes and it is important that the level of the molten salt does not drop below the level of the bottom of the electrodes. Ensure that the leads are well out of the way of the Bunsen flame. Using long electrodes can help with this.
 * Showing that the solid zinc chloride does not conduct electricity**
 * a** Begin to heat the crucible with a low to medium Bunsen flame. Watch the leads, and the bung if you are using one, to ensure that you are not over-heating them.
 * b** The zinc chloride takes about 3 or 4 minutes to melt. It may be tempting to use a roaring Bunsen flame to speed up the melting, but if you do so the zinc chloride can form a crust over the top.
 * c** As the salt melts, the bulb will light up and/or the ammeter will give a reading. Turn the Bunsen down a bit at this point. There will be some heating effect from the electric current which may be enough on its own to keep the zinc chloride molten (as in the industrial electrolysis of aluminium oxide.)
 * d** Bubbles of gas will be seen at the positive electrode. The gas can be confirmed as chlorine by holding moist indicator paper close to the bubbles - it will go red and the edges may start to bleach. A more convincing test is to use moist starch iodide paper which will go black. It is also possible to see crystals of zinc forming on the negative electrode. These can form a bridge across the electrodes, effectively shorting them.
 * e** Electrolyse the molten salt for about 15 minutes, with the current adjusted to about 0.5 A. Check every few minutes that the current remains roughly constant as there is a tendency for it to slowly increase.
 * f** After 15 minutes, turn off the power pack and Bunsen burner and remove the electrodes from the crucible. If this is not done while the salt is still molten the electrodes will stick.
 * g** Leave the crucible to cool for about 10 minutes. You may be able to see zinc crystals on both the electrode and on the surface of the mixture in the crucible.
 * Separating the zinc**
 * a** When the crucible is cool to the touch, put it into a beaker of distilled water. (If the water is at all basic like most hard tap waters, the zinc ions will flocculate forming large particles which are far harder to remove from the zinc metal.) The zinc chloride will dissolve (which may take some time) and can be decanted off. Swirl the beaker which will cause the zinc metal to concentrate in the centre of the beaker and decant off most of the liquid.
 * b** Filter the remainder. Dry the pieces of metal carefully between further sheets of filter paper and then test with a circuit tester to prove that you have a metallic product.

Observations: The first time heating up the zinc chloride it did little, but when seeing it today the zinc chloride had formed a solid layer on the bottom of the beaker, with a small amount of liquid above it. The liquid appeared slightly thicker than water. The beaker of zinc chloride was heated until it boiled, then the power source was turned on. At first the current was around 1.1, but as the temperature decreased so did the current, another interesting thing is that the voltage of one side of the power supply was lower than the other considerably. When cooled down the substance in the beaker crystallized into a strange shape with a foamy texture. Adding water to this caused it to rapidly increase in temperature until it was very hot and the crystals started to desolve.

The product of the electrolysis, presumably Zinc, was in the form of a powder. This powder, when tested with a multimeter, was proved to conduct electricity. This means that the experiment was successful in that I obtained a product that conducts electricity.

During this experiment I found that the preparation and observation of an experiment is much more work when you do it alone. This particular experiment was not too hard as it mainly involved observing the electrolysis.

Conducting this experiment helped me learn how to better prepare and also my understanding of electrolysis. I found it very interesting while observing the process. Unfortunately there is a lacking amount of resources online about electrolysis of zinc chloride so my understanding of what goes on in an atomic level is not quite as much as I would like. The product and what goes on during electrolysis is interesting, but I would like to learn about it on an atomic level.