Water Hydration Lab Report

Introduction Hydrate is any compound containing water, in this practice, we approach hydrates as crystalline solids. These solids contain a fixed amount of water molecules as part of the crystalline structure. Water is a very common chemical compound on earth. Some other chemicals, when exposed to the water that is always in the atmosphere, have the characteristic that they can either absorb the water onto the surface of the same compound or they include it in their structure This phenomenon later forms a complex in which the water molecule generally bonds with the cation in ionic substances. This water that is present inside these substances is called water of hydration or water of crystallization. The nomenclature for said hydrated salts is written with a dot between the salt and the moles of water associated with the compound. Dehydration, on the other hand, is a process by which hydrated salts lose their waters of hydration. This can be done by different techniques. The efflorescence process is when the compound loses its waters hydration rather easily when it is exposed to a dry environment and produces powdery crust. Some other cases are when the water is loosely bound to the salt, thus, allowing the water to be easily removed by applying heat to form the anhydrous salt (without water) Some hydrates, however, have the water molecules so tightly held together that they will start to decompose to produce NO2 before losing their waters of hydration. Materials and Methods ● 1 potato (small or medium size) ● 3 containers for water (deep enough to hold about a half-inch of water) ● Cutting board ● Knife ● Salt (2 tablespoons) ● Sugar (2 tablespoons) ● Water ● Piece of paper ● Pen, pencil, or marker Using the cutting board, knife, and potato, we cut the potato into three pieces of roughly the same size. Then we placed equal amounts of water in each one of the containers and in two containers we placed salt and sugar, respectively. We stirred it up to create a solution between the two. Afterward, we placed a potato slide into each one of the containers with solution. We waited 20 minutes, then we waited 40 more to equal to an hour before revising the contents of the containers. - Personal safety equipment - Safety goggles and proper clothing required. - Wash hands when leaving the laboratory. - Eye exposure: Immediately flush with fresh water for at least 15 minutes. - No food or drink in the laboratory. - Gloves to help prevent contact. Results Add some images from the experiment at home. Figure 1. Two potatoes after being surrounded in salt water (left) and normal water (right) for 20 minutes. Figure 2. Bits of potato sunk in plain water (left), sugar water (middle), and salt water (right) for 1-2 hours. -Explain the differences in the potato with the 3 solutions used (water, salt solution, sugar solution) The potato dipped in water came out almost exactly as it came in. It had a hard texture and it was rugged on the edges where there was no peeling. The potato dipped in the sugary solution had its structure be less rigid and it had a softer texture to it. The potato dipped in salt solution was very similar in texture to the sugar; but it was more softer in comparison. It also fell apart easier. -Explain which is a better dehydrator in those 3 solutions used and why. In this experiment, dehydration is being replicated by osmosis. Osmosis works by having two salt solutions of different concentrations. The one solution which has a lower salt concentration will grant part of its water to the solution with higher salt concentration. A semipermeable membrane is required for this process to occur. In the same manner, the dehydration happening in the potato is due to this. The solution with salt is more effective than the one with sugar, because salt is more “pure” for the sense being used for this experiment. The solution with water has almost no change because in this case, the potato is the one with higher salt concentration, so quite the contrary, it sucks up water. The sugar is just a minor effect of what the salt accomplishes. As the potato gives up part of its water [We can also write this as potato + salt solution -> potato (less water) + salt solution (more water)], it gives the salt solution that water to try and equal the salt concentration in both solutions. -Explain the phenomenon of hydration and dehydration in this experiment and compare it with what happens in our body. Hydration is what happens when dipping the potato in water. Essentially, the potato comes out with more water inside of it. Dehydration is what happens when we leave it in the salt solution. Likewise, it comes out with less water inside of it. Our body is much more complicated. We expel salts in our urine and sweat, but we need those salts to live as well. However, we require a certain amount of both to function correctly. Once we lose water, by force of sweat and evaporation, the salt produced as waste in our cells doesn’t get a chance to expel, so it remains there and we become dehydrated, once this happens, there are several problems with the way our cells respond. Discussion It is a fair assumption to say water is everywhere; so does it in chemistry. Water is also the most popular solvent amongst substances. Water hydration is vital when reviewing crystals and salts. Especially since salts tend to crystallize by grabbing unto water. It is here that it is important, since a lot of reactions deal with salts, salts are related to hydration and so we must review it. However, this is one sense of the word hydration. We can also review hydration as part of all living beings. As said in popular culture, water is the source of life. And this is quite true in most of its sense. A lot of organisms have gotten around the problem of conserving water. Those who don’t will be another corpse lying in the savanna or desert in the searing heat rays of the sun. It is of vital importance to humanity as well. Water is important in many sectors, but it is vital to life. Exercise makes us move and sweat and lose water and salt. People die due to dehydration as well. Even standing around makes us lose water. Hydration and dehydration are equally important. Be it in life or be it in compound we study using life. Conclusion In this practice we learned how the processes of hydration and dehydration Questions and Exercises 1. Why you should avoid heating the crucibles to a red glow when dehydrating a sample? - Because when it gets to that glowing redpoint the salt can start to decompose and the water percentage too high. 2. Why you should wait to weigh the crucible with the anhydrate salt until this one gets cold? - Because the heat from the crucible warms the surrounding air. The air rises and cools down again, which causes the phenomenon known as convection current, this current will cause an unsteady reading while measuring. 3. If you heat copper sulfate pentahydrate too long or at too high a temperature, what compound(s) is formed? HINT: Consider temperatures THAT YOU CAN REALLY ACHIEVE under experimental conditions at our laboratory. - The waters of hydration are released from the crystal and they then form water vapor. When it is hydrated it looks medium blue, and it is dehydrated, it turns light blue. CuSO4•5H2O(s) heat→ CuSO4(s) + 5H2O(g) 4. A student is dehydrating a sample and runs out of time at the end of the laboratory. She then decides to come back the following morning to finish her work. The student takes her sample out of the drawer and masses the sample. She then proceeds to calculate the % water in her sample. What are the problems she will encounter with her answer? How could she have avoided these problems if she had to mass the crucible the following day? - The sample needs to be repeated. Since it was left overnight, the student could encounter some problems related to the rapid drying of wet samples and also the disadvantage of ice crystal formation due to the evaporation of the water at reduced pressure. 5. A student heats 5 grams of a sample in a crucible; he gets distracted and does not notice that part of the sample pops out of the crucible onto the counter. How would this type of error affect the moles of water calculated in the student’s report? - The result that will be obtained will be skewed because the student lost part of the total moles of the sample. 6. Given that the molar mass of Na2SO4 · nH2O is 322.1 g/mol, calculate the degree of hydration. - 7. 79 grams of CaCl2⸱2H2O are heated up to dryness (MW of dihydrate = 147 g/mol). What is the remaining mass of the salt? 8. A sample of Na2CO3 has a mass of 9.47 g before heating, but after heating, the mass is found to be 6.872 g. Determine the formula of the hydrate and then write out the name of the hydrate. 9. 18.35 g of a hydrate of magnesium carbonate were heated, without decomposing the carbonate, to drive off the water. The mass was reduced to 8.97 g. What is the formula of this hydrate? 10. A sample of 237 g of Manganese sulfate (MnSO4⸱? H2O; MW=223.54 g/mol) is heated up to dryness. The analysis indicates that it lost 32.21 % of the mass after the heating. How many grams and moles of water were evaporated and what would be the molecular formula for this hydrate? - 11. 37.4 g of magnesium sulfate are left after complete dehydration of magnesium sulfate heptahydrate (MW=246.5 g/mol). What was the original weight of the sample before dehydration? -