Determination of a Chemical Formula

CHEM 1105 Experiment 4 termination of a Chemical enactment Introduction When corpuscles of one element conflate with those of a nonher, the combining proportionality is typically an integer or a easy fraction. The simplest verbalism of a compound expresses that atom ratio. When two or more elements atomic number 18 present in a compound, the order still indicates the atom ratio. To happen upon the canon of a compound we need to find the great deal of each of the elements in a weighed standard of that compound.For example, if we resolved a adjudicate of the compound NaOH weighing 40 grams into its elements, we would find that we obtained just ab surface 23 grams of sodium, 16 grams of oxygen, and 1 gram of hydrogen. The sample of NaOH contains equal numbers of Na, O, and H atoms. Since this is the case, the atom ratio NaOH is 111, and so the simplest formula is NaOH. In terms of moles, we gift one mole of Na, 23 grams, one mole of O, 16 grams, and one more of H, 1 gra m. From this kind of argument we foot conclude that the atom ratio in a compound is equal to the mole ratio.We get the mole ratio from chemical analysis, and from that the formula of the compound. In this experiment, we testament use these principles to find the formula of the compound with the general formula CuxCly zH2O, where x, y, and z are integers which establish the formula of the compound. The compound we allow study is called shit chloride hydrate. We first drive step up the water, which is called hydration. This occurs if we gently heat the sample to a little over speed of light*C. The compound formed is anhydrous (no water) pig chloride.If we subtract its batch from that hydrate, we fag patch up the mass of the water that was driven off, and using the molar mass of water, find the number of moles of H2O that were in the sample. Next, we need to the find every the mass of copper of chlorine in the anhydrous sample we have prepared. (It is easier to find one mass and find the other by difference. ) We do this by dissolving the anhydrous sample in water, which gives us a green solution. To that solution we resume some aluminum metal wire, which will react to the ions, converting them to copper metal. As the reaction proceeds, copper metal will appear on the aluminum wire with typical red-orange color. When the reaction is complete, we choose the excess Al, separate the copper from the solution, and weigh the dried metal. From its mass we can calculate the number of moles of Cu in the sample. We find the mass of Cl by subtracting the mass of Cu from that of the anhydrous copper chloride, and from that value determine the number of moles of Cl. The more ratio for CuClH2O gives us the formula of the compound. Experimental Weigh a clean, dry crucible, without a conduct, accurately on the analytical balance. Place or so 1 gram of the stranger hydrated copper chloride in the crucible.Then weigh the crucible and contents on the balance. Enter results on the Data page. Place the uncovered crucible on a clay triangle supported by an iron ring. arc your Bunsen burner away from the crucible, and adjust the burner so that you have a slender flame. Gentely heat the crucible as you more the burner back and forth. Do not overheat the sample. As the sample warms, the color will change from blue green crystals to the anhydrous brown form. After all the crystals are brown, remove the burner, cover the crucible to minimize rehydration, and let poise for 15 minutes.Finally, weigh the cool uncovered crucible and contents. Transfer the brown crystals in the crucible to a 50-mL beaker. Rinse out the crucible with two 5-mL portions of distilled water, and add rinsings to the beaker. Swirl the beaker to brush off crystals. The color will change to cyan as the copper ions are rehydrated. Take about 20cm of 20-guage aluminum wire (0. 25g) and form the wire into a loose spiral coil. Immerse the coil into the solution. As the copper ions are reduced, the color of the solution will fade. The reaction will take about 30 minutes to complete.The solution will be colorless and close of the copper metal that was produced will be on the Al wire. add together 5 drops of 6M HCl to dissolve any insoluble Al salts and clear up the solutions. Use your glass stirring rod to remove the copper from the wire. When finished, govern the wire aside. In the beaker, you now have metallic copper in a solution containing aluminum salt. Next, we will use a Buchner funnel to separate the copper from the solution. Weight accurately a dry penning of filter story that will fit the Buchner funnel, and record its mass. Put the paper on the funnel apply light suction as you add a few mL of water to ensure a obedient seal.With suction on, decant the solution into the funnel. Wash the copper metal thoroughly with distilled water, past transfer the wash and all of the copper to the funnel. Rinse the copper of the paper once more and turn off suction. Add 5-mL of 95% ethanol to the funnel. After a minute or so, turn suction back on. Draw air through the funnel for about 5 minutes. With your spatula, lift the filter paper from the funnel. Dry the paper and copper chthonian a heat lamp for 5 minutes. Allow it to cool to room temperature and then weigh it accurately. Results Atomic potentiometeresCopper (Cu) 63. 55 Chlorine (Cl) 35. 45 Hydrogen (H) 1. 008 Oxygen (O) 16. 00 Mass of crucible 24. 374 g Mass of crucible and hydrated sample 24. 881 g Mass of hydrated sample 0. 507 g Mass of crucible and keep sample 24. 763 g Mass of dehydrated sample 0. 389 g Mass of filter paper 0. 260 g Mass of filter paper and copper 0. 430 g Mass of copper 0. clxx g No. mole of copper 0. 003 moles Mass of water evolved 0. 118 g No. moles of water 0. 007 moles Mass of chlorine in sample (by difference) 0. 219 g No. moles of chlorine 0. 006 molesMole ratio, chlorine copper in sample 21 Mole ratio, water copper in hydrated sample 21 For mula of dehydrated sample CuCl2 Formula of hydrated sample CuCl2 2H2O Discussion The significance and relevance of the experimental results is that I was able to determine the chemical formula for the unbeknown(predicate) compound, which was copper chloride hydrate. By finding out the mole ratio, I was able to find out the chemical formula. My results were precise and accurate. My results were expected, and gave me the answer CuCl2 (dehydrated sample) and CuCl2 2H2O (hydrated sample).Conclusion The experiment went as planned. During dehydration, the color changed from blue-green to brown (anhydrous), and returned back to blue-green when water was added. When the aluminum wire was added to the solution, the copper ions were reduced to the metal, and the wire was changed to a red-orange color. From the mass calculations of the samples, I was able to find the number of moles. With mole ratio of the hydrated and dehydrated, determining the chemical formula for each was easy. The concl usion is that it is possible to find the chemical formula of an unknown compound.