Lab 9 Empirical Formulas Section Date Prelab Questions 1. what is the empirical

Question

Lab 9 Empirical Formulas Section Date Prelab Questions 1. what is the empirical formula of glucose, C ? 0 2. Magnesium oxide is made up of magnesium and oxygen. To synthesize magnesium oxide, magnesium is placed in a container and heated. Where does the oxygen come from? in buming bF masnes fum oyuen Comas 2 Ma r02 3. In Part A, where does the water in the test tube come from? 4. In Part B, why is water added to the ash residue and then heated? A 1558-g sample of hydrated magnesium sulfate (Mgso) is heated to leave a residue weighing 7.61 g. What is the formula of the hydrate? 5. (MgSO 7H,0) 6. A 2.34-g sample of copper dust is placed in a 24.62-g crucible and heated red hot to form a copper- oxygen compound. After heating, the crucible and product weigh 27.55 & What is the empirical formula of this copper-oxygen compound? Instructor's Initials Lab 9 105

Explanation / Answer

Weight of MgSO4 with hydrate = 15.58 gm

Weight of MgSO4 without hydrate = 7.61 gm

(Molar mass: 120.366 g/mol)

Moles of MgSO4 was present = 7.61 / 120.366 = 0.06322 Moles

Weight of water = 15.58 - 7.61 = 7.97 gm  

Moles of Water = 7.97 / 18 = 0.4427

Ratio of Moles MgSO4 and Water = 0.06322 : 0.4427 = 1 : 7

Hence Molecular formula of hydrate = MgSO4.7H2O

Question 6

Weight of Copper = 2.34 gm

Moles of Copper = 2.34 / 63.54 = 0.03682 Moles

Weight of copper with crucible = 2.34 + 24.62 = 26.96 gm

Product of Copper oxide after rxn = 27.55 gm

Product of Copper Oxide = 27.55 - 24.62 = 2.93 gm

Weight of Oxygen added = 0.59 gm

Moles of water = 0.59 / 18 = 0.03277 Moles

Almost equal Moles of Copper and water are present

Hence Molecular formula of Copper oxide = CuO

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