Percentage Composition by Mass of Magnesium Oxide Essay

Percentage composition by mass of magnesium oxide – Report Objective: To measure and calculate the ratio of magnesium to oxygen in magnesium oxide. To compare the lab ratio to the percent composition calculation based on the formula. Hypothesis: Based on the law of definite proportions, the percentage composition of magnesium oxide should be around 60% magnesium and 40% oxygen. Materials: * Goggles * Centigram or analytical balance * 2-4 cm magnesium ribbon * Steel Wool * Porcelain crucible and lid * Bunsen Burner * Retort Stand * Ring Stand and Clamp * Clay Triangle * Crucible Tongs * Glass Stirring Rod * Distilled Water Calculations + Observation: Please see the back of the report. Discussion: B) The fact that magnesium oxide was formed, which is a new substance, proved that a chemical reaction had taken place. E) Yes, the law of definite proportions is valid, because most of the other groups that had not encountered as many errors as us and they had more accurate results which were closer to the predicted compositions according to the law. The rest had similar results to us which proves that their errors were similar to ours. H) The white film on the surface of the magnesium was polished because it prevents reactions of magnesium and gas elements in the air. This was necessary because we wanted magnesium to react with oxygen and therefore had to remove the white film. Conclusion: J) Yes, the law of definite proportions is valid, because most of the other groups that had not encountered as many errors as us had more accurate results. The rest had similar results which proves that their errors were similar as well. Sources of error: You have to be very precautious while doing this experiment. Here are reasons/possible errors that could have been encountered: * The magnesium oxide could have been lost through the crucible during the heating process. This could result in the loss of the product. To prevent this, the lid should be set slightly off-center on the crucible so that only the air goes in. * When the glass stirring rod was used to crush the magnesium, there is a high chance that the magnesium oxide could have been left on it before adding the water, resulting in the loss of product. To prevent this, the stirring rod should be held above the crucible and then pour the water slowly on to the end of the stirring rod so that the water would run down into the crucible while dragging the MgO from the stirring rod. * Magnesium could have not reacted with oxygen completely. * The crucible might be left dirty with other particles in it that could have made variations in the MgO reaction. * The water could be contaminated. * All water might not have evaporated. * Magnesium having not been crushed completely into powder after reaction. * Rushing through experiment because of lack of time. * Chance of Problem with weighing scale. * Crucible had extra weight due to extra contents that were unseen.