Shania Washington August 28, 2014 Experiment 2 The Determination of a Chemical Formula CHEM 1315-014 Purpose of the Experiment & Techniques: The purpose of this lab is to determine the chemical formula for a hydrated compound called a copper chloride hydrate. A chemical formula is made up of letters and subscripts that give the amounts of the elements in a substance. This compound contains the elements chlorine, copper, and water molecules that are locked in the solid compounds crystal structure. The chemical formula will be found using John Dalton’s law of definite proportions, which is when “every chemical compound contains fixed and constant proportions (by weight) of its element.” (Britannica) That means we will be finding amount …show more content…
About a gram of the sample will be weighed, placed into the crucible, and weighed again all together. All large pieces will also be broken up with the spatula. The crucible will be set up snuggly on the clay triangle (and tipped slightly away). The bunsen burner will be ignited with a striker (away from the person and crucible) and then slowly moved back and forth under the crucible to heat it. The sample should be heated an extra two minutes after the color changes to brown from a blue-green. After removing the crucible we will allow it to cool and then find its mass. Next the sample will be transferred to a beaker and the crucible will be rinsed out with 8 mL aliquots of distilled water and added to the sample. We will stir the mixture to help it dissolve (noticing the color change back to blue-green). The aluminum wire will then be twisted around our fingers(into a few coils) and completely submerged in the solution. After about 30 minutes the solution will be colorless and the copper will be on the aluminum wire. Five drops of the 6 M Hydrochoric Acid solution will be added to help dissolve any of the aluminum salts that have gone into the mixture (which will help make it clear). We need to make sure to be extra careful with the Hydrochloric Acid so we are not burned. With a stirring rod we will collect as much of the copper from the wire and put it back into the beaker, then take the wire and clean off the remaining copper with the distilled water. Two drops of the Hydrochloric Acid can be used if needed to clean off the rest of the copper from the wire. The wire will be put on a Kimwipe and the copper will then be collected and washed. A Büchner funnel will be set up to be used as a vacuum filter. The ring stand will hold a clamp around the flask which will have a funnel in the top and a tube attached to the vacuum