Concept:The limiting reactant is identified by dividing the supplied amount (moles) by the stoichiometric coefficient required by the balanced equation.
Formula:$$ \text{Limit} = \text{Smallest value of } \left( \frac{\text{Moles}}{\text{Coefficient}} \right) $$
Solution:- The balanced equation is: \( 2\text{A} + 1\text{B} \rightarrow \text{Product} \).
- This means every 1 mole of B requires exactly 2 moles of A to react completely. A is consumed twice as fast as B.
- We are told we have "equal moles" of A and B. Let's assume we have 1 mole of A and 1 mole of B.
- Test for Limiting Reactant:
- For A: \( 1 \text{ (available mole)} / 2 \text{ (coefficient)} = 0.5 \).
- For B: \( 1 \text{ (available mole)} / 1 \text{ (coefficient)} = 1.0 \).
- Since 0.5 is smaller than 1.0, Reactant A is entirely consumed first, leaving half of Reactant B unreacted. Therefore, A is the limiting reactant.
Why other options are incorrect:- Reactant B: Incorrect, as it is consumed much slower than A and will be left in excess.
- Reactant A and B / No limiting reactant: This would only be true if they were supplied in a 2:1 stoichiometric ratio, not a 1:1 "equal moles" ratio.
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