# The City Essay

255 Words2 Pages
Name: Anh Lan Do Course: CHE-131-92L Date: Feb 24th, 2010 General Chemistry 1 Experiment 4 Percent Composition of a Compound Professor Robert M. Cady Questions: 1. According to the law of definite composition, elements form compounds in the same ratios by mass each time the compound is produced. Using the theoretical percent by mass of magnesium in MgO, calculate the mass of oxygen that will combine with 12.25g of Mg and the mass of MgO that will be formed. 2. Which compound has the greatest percentage by mass of Magnesium? a) MgCl2 : * MgCl2 = 24.31g + (2* 35.45g) = 95.21g Percentage by mass of Mg: * (24.31g/ 95.21g )* 100= 25.53 % b) Mg(NO3)2 : * Mg(NO3)2 = 24.31g + 2* (14.01g+(16.00g*3)) = 148.33g Percentage by mass of Mg: * ( 24.31g/ 148.33g) * 100 = 16.39% c) Mg3(PO4)2 : * Mg3(PO4)2 = (24.31g *3) + 2( 30.97g + (16.00g * 4)) = 262.87g Percentage by mass of Mg: * ( 72.93g/ 262.87g) * 100 = 27.74% d) MgSO4 : * MgSO4 = 24.31g + 32.07g + (16.00g * 4) = 120.38g Percentage by mass of Mg: * (24.31g/ 120.38g) * 100 = 20.19% The compound has the greatest percentage by mass of Magnesium is Mg3(PO4)2 3. Magnesium sulfide is 43.1 % Mg by mass. How many tons of Sulfur can be produced by the thermal decomposition of 20.5 tons of magnesium sulfide? Lab 4 Objective: The goal of the experiment is to find the mass of