Eichenblatt Sam Post Lab2 wri te up Lab 2 was used to find the identity of an unknown substance, and this was done in two scenarios. The first part was designed for the students to find the percent of water in an u nknown hydrate by heating the substance until all of the water evaporated out of the substance. Then the student would weigh the substance and find the weight after evaporation. The ratio between the weight of substance before and after dehydration is compared to the ratios of known substances and if there is a matching ratio than we know w hat that substance is. The second part of this experiment was to show the use of s toichiometry in the lab. We were given iron and copper sulfate. Using stoichiometry we created a chemical reaction, and used the ratio of moles, and the unique blue color of copper sulfate to find the oxidation state of Fe. In the fi rst part, the focus of the experiment was t he law of conservation of mass. This law states that the total of mass a closed system will s tay constant. This means if we were to heat up the hydrate in a closed container and let t he water vapor accumulate inside the container the total mass would not change. This also means that the mass lost during the heating process was that of water. So we know how m uch water was in the hydrate and using this we can find what the substance was. While i n theory this should work perfectly, there is plenty of room for error. The scale could be m iscalibrated, the heating process could be too short, or the hydrate could have decomposed. Ignoring that these errors might have come into play, my group found that our
hydrate was CaSO4. Our anhydrate to hydrate ratio was 0.836 which means that the hydrate lost 16.4% water. CaSO4 has a ratio of .7909, the closest to our ratio. I am not very confident in these results because the ratio for CuCl2 is very close to that of CaSO4, and our results are about 4% off from the actual mass ratio.