Chemical Formula of a Hydrate

Chemical Formula of a Hydrate Objective: The objective is to complete the dehydration of a hydrate by separating it into an anhydrate and water molecules. Also, to calculate the percentage of water in the hydrate and to calculate the hydrates formula using various formulas in order to determine this information. Introduction: The number of atoms of each element that compose a compound is indicated by the chemical formula. A chemical formula can be written both as empirical and as molecular. The Empirical formula is the formula composed of the simplest or most reduced ratio of the elements within a compound. The Molecular formula is the formula that says how many atoms of each element are within a compound. An example of an empirical formula is H2O where it is in its most simplest form whereas H4O2 can still be simplified into H2O. H2O also composes a part of a hydrate. Hydrates are compounds that are composed of salts chemically bonded to water molecules. The bond between the metal cation and the water molecules is direct in which some metals can form bonds with multiple hydrates. Heating causes this bond to break and in turn can create an anhydrate which simply means without water. This can be used in order to determine the weights of both the hydrates and the anhydrates in order to determine ratios and to determine the formula of the hydrate which is written like saltᐧxH2O. Chemicals used within this experiment were MgSO4, magnesium sulfate, and H2O, water. While H2O is not much of a safety concern, it is important to handle magnesium sulfate with care as it can become hazardous when not used correctly. Results and Discussion: In order to obtain the weight of the salt alone, the crucible was weighed with and without salt in it and then heated up to get all the hydrate out. The weight of the empty crucible was 21.59 grams and the weight of the crucible with salt in it was 23.91 grams meaning the weight of the salt alone is 2.32 grams found using subtraction. After the heating process and experiment, the weight of the salt was 1.12 grams. Weight of empty crucible 21.59 grams Weight of crucible with salt 23.91 grams Weight of salt 2.32 grams Weight of crucible with salt after heating 22.72 grams Weight of salt 1.13 grams Weight of crucible with salt after waiting 5 minutes 22.71 grams Weight of salt 1.12 grams Table 1: Mass of salt within the experiment Further calculations were used to determine the percentage of water within the hydrate and the formula of the hydrate. In order to determine the percentage of water, first the mass of the anhydrate was subtracted from the mass of the hydrate which gives the mass of H2O. The mass of H2O then is divided by the mass of the hydrate multiplied by 100 which gives the percentage of water. The calculated percentage of water in the hydrate came out out be 51.72%. To determine the formula of a hydrate the mass of the anhydrate and water must be converted to moles. The ratio is set up moles of anhydrate: moles of water and then was divided on both sides by the smaller number of moles in order to get whole numbers. The ratio during this experiment was 1:7.17. For every mole of anhydrate, there is 7.17 moles of water. This number is a bit higher than the actual value which is 1:7 causing the percentage error to be 1.02%. This could have been caused by improper weighing during the experiment or possibly that all the moisture wasn’t entirely out of the crucible causing the mass to be higher. Many different possibilities could have caused the moles of water to be higher but it is very close to the actual number. Mass of hydrate (g) 2.32 grams Mass of anhydrate (g) 1.12 grams Mol of anhydrate (mol) 0.0093 mol Mass of H2O eliminated (g) 1.2 grams Mol of H2O eliminated (mol) 0.0666 mol Formula of hydrate MgSO4ᐧ7.17H2O Percentage of H2O in hydrate 51.72% Percentage error 1.02% Table 2: Hydrate and Anhydrate information The objective was accomplished as seen in Table 2 where the formula of the hydrate was calculated and the percentage of water was found within the hydrate. Conclusion: The objective was fulfilled as the dehydration of a hydrate was completed and the calculation of the percentage of water within the hydrate. The calculated percentage of water within the hydrate was 51.72% and the final formula of the hydrate was MgSO4ᐧ7.17H2O.