Which characteristic of enzymes allows it to be highly specific in the reactions they catalyze?

You are performing an experiment in a lab to attempt a new method of producing pure elements from compounds. the only problem is that you do not know what element will form. by your previous calculations you know that you will have 6.3 moles of product. when it is complete, you weigh it and determine you have 604.4 grams. what element have you produced?

Find the number of grams of hcl needed to react completely with .50 moles of magnesium.

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.