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Lesson 4.2 Limiting and Excess Reactants

Limiting and Excess Reactant

In a chemical reaction, the limiting reactant determines the amount of product formed, while the excess reactant remains unreacted. This lesson explores how to identify the limiting reactant, calculate remaining excess reactants, and determine product yield, essential for understanding reaction efficiency and resource utilization.

📌 Instructions:
✔ Choose the best answer for each question.
✔ Show your work for calculations if needed.
✔ Click Submit to check your answers and explanations.

Let’s see how much you’ve learned—good luck!

What is the limiting reactant in a chemical reaction?

The reactant that remains after the reaction

The reactant that is completely used up first

The reactant with the highest mass

The reactant that forms the most product

None

What is the excess reactant in a chemical reaction?

The reactant that determines the product amount

The reactant that remains after the reaction is complete

The product of a reaction

The reactant that is completely used up

None

In the sandwich analogy: If you have 10 slices of bread and 6 slices of cheese, and each sandwich needs 2 slices of bread and 1 slice of cheese, what is the limiting reactant?

Cheese

Bread

Sandwich

Both bread and cheese

None

What is the first step in identifying the limiting reactant in a reaction?

Convert given reactant amounts to moles

Write the balanced chemical equation

Compare mole ratios

Identify the excess reactant

None

If you have 4 moles of H2 and 3 moles of 02 for the reaction 2H2 + O2 → 2H20, what is the limiting reactant?

H2

O2

H2O

Both He and O2

None

What determines the maximum amount of product that can be formed in a reaction?

The excess reactant

The limiting reactant

The product itself

The total mass of reactants

None

The excess reactant is the one that:

Is completely consumed first

Produces the least amount of product

Is left over after the reaction

Determines the reaction rate

None

True or False: The limiting reactant is always the reactant present in the smallest mass.

True

False

None

Which of the following best describes the limiting reactant concept?

It is always the reactant with the lowest mass

It limits the reaction by stopping when it runs out

It is the reactant that remains unused

It is only important in theoretical calculations

None

What should you use to compare reactants when determining the limiting reactant?

Their masses in grams

Their chemical formulas

The mole ratios from a balanced equation

The number of atoms in each reactant

None

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