Question

If 3.0 moles of X and 5.0 moles of Y react according to the hypothetical reaction below, how many moles of the excess reactant will be left over at the end of the reaction?

[X + 2Y rightarrow XY₂]

a) 0 moles
b) 1.0 moles
c) 2.0 moles
d) 3.0 moles

Answer 1

The excess reactant left over at the end of the reaction is 3.0 moles.

Step-by-step explanation:

To determine how many moles of the excess reactant will be left over at the end of the reaction, we need to identify the limiting reagent. The limiting reagent is the reactant that is completely consumed in the reaction, thus determining the amount of product formed.

In this reaction, the stoichiometric ratio is 1 mole of X reacts with 2 moles of Y to form 1 mole of XY2. Since we have 3.0 moles of X and 5.0 moles of Y, X is the limiting reagent because it will be completely consumed after reacting with 2.0 moles of Y.

Therefore, the excess reactant is Y, and after the reaction, there will be 5.0 - 2.0 = 3.0 moles of excess Y left over.