Theoretical Masses of Products Flashcards

All 5 cards in this deck

What is meant by the maximum theoretical mass of a product?

The mass of product that would be made if all the reactant were converted, with no losses and no side reactions.

What are the steps to calculate the theoretical mass of a product from a given mass of reactant?

e.g. mass of MgO from 2.4 g of Mg in $2\mathrm{Mg} + \mathrm{O_2} \rightarrow 2\mathrm{MgO}$ ($A_r$ Mg = 24, $M_r$ MgO = 40)

1. Moles of reactant $= 2.4 \div 24 = 0.1$ mol
2. Use the equation ratio $2:2$, so moles of MgO $= 0.1$ mol
3. Mass $= 0.1 \times 40 = 4$ g

Which piece of information from the chemical equation is needed to convert moles of reactant into moles of product?

The balancing numbers (the mole ratio of reactant to product in the balanced equation).

True or false? The theoretical mass calculated from a balanced equation allows for product lost during filtering and drying.

False. The theoretical mass assumes no losses at all; losses are why the actual yield is lower.

When a reactant is in excess, which reactant's mass is used to calculate the theoretical mass of product?

The reactant that is not in excess (the limiting reactant), because it is used up first.