Final answer:
The question seems to have a typo or a misunderstanding because converting magnesium bromide directly to benzoic acid isn't a standard reaction. Theoretical yield refers to how much product can be expected from a reaction under perfect conditions. For reactions like reducing boric oxide with magnesium or electrolyzing MgCl₂, the theoretical yield of the products can be calculated based on the reactants consumed.
Step-by-step explanation:
The theoretical yield of magnesium bromide converting to benzoic acid isn't given in common stoichiometric reactions, as the conversion directly from magnesium bromide to benzoic acid is not a typical chemical reaction. However, we can discuss the concept of theoretical yield with respect to other given reactions. Theoretical yield is the amount of product that would be formed if every mole of reactant reacts to form the product.
For example, when magnesium powder is used to reduce boric oxide, the product formed is boron. The grams of magnesium and boric oxide used in the reaction would determine the theoretical yield of boron.
In the case of electrical current passed through a MgCl₂ melt, the theoretical yield of magnesium will be affected by the amperage and time of the reaction as well as the efficiency of the process. If the yield of magnesium is 85% of the theoretical yield and the current passed is 100,000 A for 1.00 h, then you would calculate the theoretical yield first and then take 85% of that value to find the actual yield.