Stoichiometry concept check:\nIn any chemical reaction, the “limiting reactant” determines which key outcome?

Introduction / Context:
In stoichiometry, the limiting reactant is the reagent that is consumed first and thereby caps how much product can form. This concept applies across batch and flow reactors and is fundamental to yield, feed preparation, cost estimation, and waste minimization.

Given Data / Assumptions:

• Balanced chemical equation available.
• Feeds may be off-stoichiometric (excess of one or more reagents).
• No side reactions considered for the basic definition.

Concept / Approach:
The equilibrium constant is a thermodynamic property determined by temperature, independent of feed ratios. The intrinsic rate constant depends on mechanism and temperature (Arrhenius), not on feed stoichiometry. In contrast, the limiting reactant defines the theoretical maximum conversion to products: once it is fully consumed, the reaction cannot proceed further regardless of other species remaining in excess.

Step-by-Step Solution:

Verification / Alternative check:
Material balance on the limiting species directly yields the maximum possible moles of product via stoichiometric ratios.

Why Other Options Are Wrong:

• (a) Equilibrium constant is not controlled by feed amounts.
• (c) Rate constant is kinetic, not stoichiometric.
• (d) Selectivity may be influenced by feeds but is not the defining role of “limiting reactant.”
• (e) Residence time is a design variable, not defined by which reactant is limiting.

Common Pitfalls:
Confusing “limiting reactant” with “rate-limiting step” in mechanisms; mixing up thermodynamic (K) and kinetic (k) parameters.

Final Answer:
The maximum possible conversion (extent of reaction).