CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
In a teaching laboratory, students perform a synthesis of magnesium oxide by heating magnesium ribbon in air. The balanced chemical equation for the primary reaction is
2Mg(s)+O2(g)→2MgO(s)
During the post-lab discussion, the instructor asks students to reflect on how chemists predict and evaluate the amount of product formed in any reaction.
(a) Define the term "limiting reactant" and explain why identifying it is essential when predicting the amount of product in a chemical reaction.
(b) Distinguish between "theoretical yield," "actual yield," and "percent yield." In your explanation, comment on how experimental design and technique can influence each of these quantities.
(c) Using the reaction above as an example, describe—at the particulate level—what happens when magnesium is present in excess. Include in your answer what is observed macroscopically and what remains after the reaction is complete.