In the reaction X + 5Y > 3Z, the problem involves 3 moles of X and 2.8 moles of Y. To determine how much X will react, it's essential to identify the limiting reactant. The stoichiometry indicates that 5 moles of Y are required for every mole of X, meaning that with only 2.8 moles of Y available, Y is the limiting reactant. Consequently, the amount of X that will actually react is based on the available Y, leading to the conclusion that not all of the 3 moles of X will be consumed. Understanding the limiting reactant is crucial for solving stoichiometry problems effectively.