In this lab, you will experimentally determine the empirical formula for magnesium oxide. You will do this by combusting magnesium in an oxygen-rich environment. To begin, you will need to determine the mass of a crucible and its lid. Make sure they are both clean and dry before you weigh them. Once you have recorded the weight of the crucible and the lid, add in the magnesium ribbon and record the combined weight. The weight of the ribbon should be about 0.5 to 0.75 grams. Do not wrap the magnesium ribbon too tightly. Air needs to get in for the reaction to take place. When lighting a bunsen burner, ensure that anything flammable, such as hair or clothing, is well out of the way. Turn on the gasfoil and then bring a light, match or lighter towards the end of the bunsen burner, and it should ignite. In order for this reaction to proceed properly, you need to make sure the bunsen burner is close enough to the crucible to heat it well. The high temperature will cause the magnesium to ignite, though first the crucible will begin to glow with the heat. Raising the lid of the crucible will allow oxygen from the air to enter the crucible. This will ignite the magnesium causing the formation of magnesium oxide. You not look directly at burning magnesium. The intense light can damage your eyes. During this reaction, you will want to ensure that oxygen gets in for the reaction to take place. You can either do this by tilting the lid off the crucible slightly to allow oxygen flow or raising and lowering the lid periodically. Be sure not to let the reaction smoke too much. Any smoke coming out of the system is actually a loss of product. Allow the reaction to proceed, periodically checking on it to see whether a nod ignition occurs when the lid is raised. When the ignition finally ceases, you know that the reaction is done. At the moment you can see that this is still glowing hot, but no ignition is taking place, so we know that the reaction is done. You can turn off the bunsen burner and leave the crucible to cool. Allow it to cool completely before proceeding with the next step. Using a medicine dropper, add a small volume of water to turn the solid in the bottom of the crucible into a thick paste. You'll do this by stirring it up with a glass stirring rod. Ensure that all the material remains within the crucible, so wipe off the stirring rod on the edge of the crucible before you complete the step. Return the crucible to the bunsen burner and heat it once again. This will complete the formation of the magnesium oxide. This process will take several minutes, but you can check on it periodically, and once it is all light gray color, the reaction is complete. After the drying process, allow the crucible to cool before weighing it. Make sure that it is cooled completely before you proceed with this step. Obtain and record the final mass of the crucible and the solid within it. Finally, clean and scrub the crucible to remove any of the solid to ensure that it is completely clean before returning it.