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Howard University General Chemistry Lab. I spring 2021- Quiz 3 (% Water in a hydrated salt) Name: Bryce Augustine

ID: 02987204

Q1. How do you know that all of the water of hydration has been removed from your unknown hydrate? Explain. You know that all of the hydrated water is removed because it will turn into an anhydrous solution. Q2. A 1.628g sample of a hydrate of magnesium iodide is heated until its mass is reduced to 1.072 g and all water has been removed. What is the formula of the hydrate? MgI2 = 1.072g = .0039 mol/.oo30 =1 H2O - .556 = .0309 mol/.0039 = 8 MgI2 (dot) 8H2O Q3. Hydrated sodium tetraborate Na2B4O7.10H2O is commonly called borax. Heated and 5.9 g of water are removed. What is the mass of the anhydrous borax? Molar mass = 381.37 g/mol Q4. 2.362 g of an unknown hydrate are heated until all the water is removed. The anhydride residue weighs 2.015 g. Calculate the percentage of water in this hydrate. 2.362-2.015 = .347g .347/ 2.362 x 100 =14.7% Q5. The chemical formula for an ionic compound of aluminum and oxygen is a. b. c. d.

AlO Al2O3 Al2O AlO2

Q6. Find the percentage composition of P in Mg 3(PO4)2 3 Mg x 24.305 = 72.915 = 27.739% 2 P x 30.973762 = 61.947524 = 23.567% 8 O x 15.9994 = 127.9952 = 48.694% Mg3(PO4)2

= 262.857

Q7. Why is the formula of the water in a hydrate separated by a dot (CoCl 2•6H2O) rather than being included in the formula (CoCl2H12O6)? This is because in a hyrdrate the water is tightly bound to compound but they are still separately their own. The dot just represents that they’re bound together.

Q8. A hydrated salt is found to have the empirical formula CaN 2H8O10. What is its dot formula? Ca(NO3)2 (dot) 4H2O...