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Determining the Empirical Formula of Magnesium Oxide and the Chemical Formula of a Hydrate

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Introduction

´╗┐Determining the Empirical Formula of Magnesium Oxide and the Chemical Formula of a Hydrate Grade 11 Chemistry (SCH3U0-B) Mr. Martin Experiment Performed on Thursday November 1st, 2012 Written by: Danny Nguyen, Feroze Nooruddin, and Nina Backa Just like pounds, feet, and dozens, the mole (units: mol) is simply yet another counting or grouping unit. To be specific, it is 6.02 x 1023 of whatever that is being counted [3]. In chemistry, the mole is used to group ions, atoms and formula units. The number of particles is valuable information, but it is much more useful if the mass of the particles is also determined. The mass and mole relationship states that a mole of any substance has a mass equal to its atomic mass [7]. In the case of a compound, it is the added value of the separate atomic masses. This value is called the molar mass (units: g/mol). For example, the molar mass of oxygen is 16.00 g/mol, and the molar mass of CO2 is 44.01 g/mol [2]. Any molecule or a compound can be defined by its molecular formula. The molecular formula provides the number of atoms present in each molecule of that compound. For example, the formula for acetate, C2H4O2, indicates that there are 2 carbon atoms, 4 hydrogen atoms, and 2 oxygen atoms in one molecule of acetate. ...read more.

Middle

sulfate can be determined. Knowing this information, it can be predicted that the percentage composition of water in the hydrate is approximately around 60%. Experiment 1: Determining the Empirical Formula of Magnesium Oxide Materials and Method for the Experiment *The procedure for this experiment can be found on pages 212 and 213 in the McGraw-Hill Ryerson textbook.* Some changes to the experiment that might change the results are: Used less amount of Magnesium than stated Experimental Results: Table 1: Qualitative Observations of the Magnesium Before reaction Grey-ish and a relatively shiny solid Product White powder, increase in temperature Table 2: Data obtained while reacting magnesium in air Mass in grams Mass of clean, empty crucible and lid 46.25 ± 0.01 Mass of crucible, lid and magnesium 46.29 ± 0.01 Mass of crucible with lid and magnesium oxide 46.45 ± 0.01 *This charts shows the results of the experiment “Determining the Empirical Formula of Magnesium Oxide”, the data is the weighing of the mass in each stage of the experiment. This data is obtained through, the weighing of the different materials. Calculations (Mass by difference): Mass of Magnesium = (Mass of crucible, lid and magnesium) – (Mass of clean, empty crucible and lid) Mass of Magnesium = 46.29grams – 46.25grams Mass of Magnesium = 0.04grams Uncertainty: General equation when calculating numbers with uncertainty: While addition or subtracting (let e represent uncertainty) ...read more.

Conclusion

sulfate and H2O can be determined in a similar manner. *Refer to the uncertainty equation on Page 3 to calculate all uncertainties. Table 6: Masses of Reactants and Product: Mass of Anhydrate copper (II) sulfate 1.56 ± 0.02 grams Mass of Hydrate copper (II) sulfate 0.73 ± 0.02 grams Mass of H2O 0.83 ± 0.02 grams To determine the chemical formula of a Hydrate: Convert all masses in to moles Mass of Element * = Number of moles 0.73 ± 0.02 grams CuSO4 × = 4.57 × 10^-3 ± 0.02 mol 0.83 ± 0.02 grams H2O × = 0.046 ± 0.02 mol Determine the lowest whole number ratio of all molar quantities: Lowest ratio= CuSO4= = 1 H20= = 4.91 = 5 *In this case, disregard uncertainties as it accounts for only a minor difference to the mole ratio. Therefore, the chemical formula for Hydrate Copper (II) Sulfate is CuSO4 × 5 H2O Determining the mass percent of water in a Hydrate of Copper (II) sulfate: Molar mass of water (H2O)____ x 100% Molar mass of CuSO4 x 5 H2O Molar mass of water= 5 * [(2 * Mass of Hydrogen) + Mass of oxygen] = 5 * [(2 * 1.01) + 16.00] = 90.1 grams Molar mass of CuSO4 = Mass of Copper + Mass of Sulfur + (4 * Mass of oxygen) = 63.55 + 32.06 + (4 * 16.00) = 249.71 grams Therefore, Mass percent of water = 90.1 grams_ x 100% = 36% 249. ...read more.

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