Chemistry Postlab Problems

Question

Why was a ceramic lid placed on the crucible once the magnesium began smoking and flaming? What error in the final empirical formula would likely have been encountered if the lid was allowed to stay off the crucible while the reaction flamed and sputtered?

Answer 1

That "smoke" is actually particles of MgO, the product. So, since you're trying to determine the empirical formula of the magnesium oxide, and you need the mass, you wouldn't have all of the product, leading to a low answer & thus incorrect results.