CHM 113 -Lab3_ How much Water is in the Hydrate

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Arizona State University, Tempe *

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113

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Chemistry

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Feb 20, 2024

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Water in Hydrates 1 How much Water is in the Hydrate? Lab Members- 1) Atlanta Das (1222600795) 2) Chris Feist (1218567233) 3) Drishti Gopal Chandwani (1225873157) 4) Khang Do (1225044184) Teaching Assistant- Soumya Dutta Date- 8th February 2023 CHM 113 - Wednesday - 6:00 pm to 7:50 pm

Water in Hydrates 2 Introduction: Hydrates are salts that have water incorporated into their crystalline structure. The salts' ability to form crystal structures and absorb water is due to the strong interaction between polar water molecules and ions in hydrates. The maximum amount of water that a salt can absorb is determined by its crystal structure and is known as water of hydration. Heating the salt can cause the water of hydration to be driven off, leaving an anhydrous residue. In this experiment we will find out how much water is present in some hydrates. We can do this by using some formulas like finding the mass% of water of hydration. mass% of water of hydration = mass of water(g) x 100% Mass of hydrated salt(g) Finding the mole ratio will also be required in order to determine the nearest whole number ratio of the water to salt. We can do this by using the formula:- Mole ratio = mol water Mol of anhydrous salt We will be finding how much water is in the following hydrates:- 1) MgSO 4 .XH 2 O 2) CuSO 4 .XH 2 O Procedure: The goal of this lab was to determine the formula of the unknown hydrates- MgSO 4 .XH 2 O and CuSO 4 .XH 2 O. As part of the protocol for this experiment, the first step is to make sure that all safety measures and equipment are accessible and suitable for use. The heating plate should be set to 450 degrees Celsius after the safety apparatus is in place. The mass of the two empty crucibles and their lids should be measured using the scale while you wait for the plate to heat up. The crucibles are then filled with hydrates and set on the heating plate when the heating plate has reached 450 degrees Celsius. A timer is set to heat for 15 minutes and cool for 2 minutes. The salt-filled crucible is

Water in Hydrates 3 then massed once it has cooled. For accuracy, this is performed twice more. Each of the three trials yields data. The solid trash is disposed of at the appropriate waste collection place when the experiments are over. The materials are cleaned, and the heating plate is switched off. Calculations and Results: Table 1: Initial Data Collection: The table below shows the weight of the salt before and after cycles 1 and 2. Name of Salt Mass of Empty Crucible Mass of Crucible with Salt Time Cycle 1 Mass of Crucible Time Cycle 2 Mass of Crucible A B 10 min heating + 5 min cooling B1 10 min heating + 5 min cooling B2 MgSO4 20.54 g 21.37 g 21.05 g 21.02 g CuSO4 37.73 g 38.32 g 38.04 g 38.08 g Table 2: Post Experiment Data Collection: This table shows the experimental mass of the hydrated and anhydrous salt and also the mass of water lost in the heating/cooling process. Name of Salt Mass of hydrated Salt Mass of Anhydrous Salt Mass of Water Lost U = B - A V = B2 - A U - V = C MgSO4 0.83 g 0.48 g 0.35 g CuSO4 0.59 g 0.35 g 0.24 g 1) % 𝑤𝑎??? = 𝐶/? * 100 a) % 𝑤𝑎??? 𝑖? 𝑀?𝑆𝑂4 = 0. 35/0. 83 * 100 = 42. 17% b) % 𝑤𝑎??? 𝑖? 𝐶?𝑆𝑂4 = 0. 24/0. 59 * 100 = 40. 68% 2) ??. ?? ????? = ?𝑎?? ?? 𝑎?ℎ𝑦????? ?𝑎?? (?)/???𝑎? ?𝑎?? * 100

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Water in Hydrates 4 a) ????? ?? 𝑀?𝑆𝑂4 = 0. 48 ?/120. 36 ?/??? = 3. 9 * 10 −3 ????? b) ????? ?? 𝐶?𝑆?4 = 0. 35 ?/159. 609 ?/??? = 2. 19 * 10 −3 ????? 3) ????? ?? 𝐻20 𝑖? ℎ𝑦??𝑎??? 𝑆𝑎?? 𝑖?: a) 𝑀?𝑆𝑂4 = 4. 87 ????? ≈ 5 ????? b) 𝐶?𝑆𝑂4 = 6. 07 ????? ≈ 6 ????? 4) Empirical Formula for MgSO4 is MgSO4.5H20 5) Empirical Formula for CuSO4 is CuSO4.6H20 Discussion: This experiment allowed the team to calculate the amount of mass percent of water within the Copper Sulfate along with finding the empirical formula of the Copper Sulfate. In order to begin the experiment, the mass difference between the crucible and a hydrate salt was discovered. This was done in two different trials, as well as for each trial having two different heating cycles of 10 minutes each at temperatures 450 ℃ . The second part of the experiment was to determine how much water from the first trial was in the hydrate by subtracting the new mass from the original mass from the heating. It is important that there is no water or residue remaining in the crucible or on the scale when taking each measurement to ensure a proper calculation. Discovering the correct measurements for the remaining Copper Sulfate as well as water that was lost in grams is important in the experiment because it is later used to determine the moles of each. The experiment was to determine the amount of moles of water which was calculated to have yielded a result of 0.35 moles and the second trial yielded 0.24 moles of water. Next, the moles of remaining dehydrated Copper Sulfate were discovered from the grams of remaining hydrate from trial one which was .83g as well as .59g from trial two.

Water in Hydrates 5 Conclusion: The goals of this experiment were to find the mass percent of H2O in an unknown hydrate and to find the empirical formula of an unknown hydrate. After conducting calculations, the final results of a mass percent of H2O could be identified for both trials; following these calculations, the lab group was also able to identify the empirical formula for both trials; This helped successfully achieve both objectives stated in the introduction of this lab, which were to find the mass percent of water in an unknown hydrate and to find the empirical formula of an unknown hydrate. The empirical formula is often used as an accurate method of calculating many chemical reactions which are very useful in everyday practice. For example in an article, “...knowing what a reaction is going to produce makes the reactions safer and more efficient to the consumer of the reaction. … In a rocket ship, the space for materials and mistakes is very limited. By knowing things like the empirical formula and some stoichiometry, it would be easy to efficiently map out how much materials the rocket needs to take and how much should be used in the reactions”(google.com).

Water in Hydrates 6 References N, H. (n.d.). Applications - determination of the empirical formula of silver oxide -harshini m. Google Sites: Sign-in. Retrieved February 8, 2023, from https://sites.google.com/site/1silveroxidelab/applications

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