Lab 3 - Determination of the Formula of a Metal Oxide PDF

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Determination of the Formula of a Metal Oxide...

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Determination of the Formula of a Metal Oxide

Purpose The goal of this lab is to find the empirical formula of a metal oxide. By doing so the law of constant composition will be demonstrated.

Procedure The procedure for this lab can be found on pages 35-39 in “General Chemistry CHE110L Laboratory Manual Fall 2019.

Data Tables Carbon Copies of data are attached to the back of this lab report. Calculations: Mass of Oxygen= Mass of Mg – Mass of Magnesium Oxide O = .171g - .111g = .06g O % of Mg = Mass of Mg/ Mass of Magnesium Oxide = .111g/.171g = 64.9% % of Oxygen = Mass of O/ Mass of Magnesium Oxide = .06g/.171g = 35.1% O # of Moles of Mg = Mass of Mg/ Molar Mass of 1 molMg = .111g/24.31g = .00704 moles Mg # of Moles of O = Mass of O / Molar Mass of 1molO = .06g/16.0g = .00375 moles O Mole Ratio= Moles of Mg/ Moles of O = .00704molesMg/.00375molesO = 2:1 ratio

% yield equation: (actual yield/theoretical yield) x 100.

Summary of Results % Mg in Magnesium Oxide

64.9%

% O in Magnesium Oxide

35.1%

Mole Ratio Mg:O

2:1

Empirical Formula of Magnesium Oxide

Mg2O

Theoretical yield of Magnesium Oxide

0.148

% Yield of Magnesium Oxide

75.0%

Conclusion The goal of this lab was to determine the formula of Magnesium Oxide. This was found by calculating the percent of Magnesium and Oxygen present in Magnesium Oxide. After finding this, the empirical formula was determined, demonstrating the law of constant composition. There may have been error if ash got stuck on the metal stirring rod, making the mass of the magnesium oxide to be less than what it should’ve been. If there was still ash on the stirring rod, the percentage of Magnesium and Oxygen may be incorrect and invalid.

Post Lab Questions Use your mass of magnesium to calculate the % yield of your reaction for the following 3 scenarios: 1. The formula of your compound is MgO (0.111/0.184) x 100 Theoretical Yield = .184 Percentage Yield = 60.3% 2. The formula of your compound is MgO2 (0.111/0.257) x 100 Theoretical Yield = .257 Percentage Yield= 43.2% 3. The formula of your compound is Mg2O (0.111/0.148) x 100 Theoretical Yield = .148 Percentage Yield = 75.0%...