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# Limiting Reactants Using Particulate Diagrams Mark as Favorite (36 Favorites)

ACTIVITY in Balancing Equations, Stoichiometry, Conservation of Mass, Limiting Reactant. Last updated July 14, 2024.

### Summary

In this activity, students will practice drawing particulate diagrams to help them determine the limiting reactant given a certain number of reactant molecules. Students’ practice with particulate diagrams will help them better visualize and understand limiting reactant calculations. The visualizations provided in this activity are helpful at all levels, from beginning chemistry students up through AP chemistry students, who will need to be comfortable with particulate diagrams for the AP exam.

High School

### NGSS Alignment

This activity will help prepare your students to meet the performance expectations in the following standards:

• HS-PS1-7: Use mathematical representation to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
• Scientific and Engineering Practices:
• Developing and Using Models

### AP Chemistry Curriculum Framework

This activity supports the following unit, topics and learning objectives:

• Unit 4: Chemical Reactions
• Topic 4.3: Representations of Reactions
• TRA-1.C: Represent a given chemical reaction or physical process with a consistent particulate model.
• Topic 4.5: Stoichiometry
• SPQ-4.A: Explain changes in the amounts of reactants and products based on the balanced reaction equation for a chemical process.

### Objectives

By the end of this activity, students should be able to:

• Use particulate diagrams to visualize what is occurring in a chemical reaction and determine the limiting and excess reactants.

### Chemistry Topics

This activity supports students’ understanding of:

• Chemical Reactions
• Stoichiometry
• Limiting Reactant
• Excess reactant
• Balancing Equations
• Conservation of Matter
• Particle Diagrams

### Time

Teacher Preparation: minimal

Lesson: 30–45 minutes

### Materials

• Student activity sheet

### Safety

• No specific safety precautions need to be observed for this activity.

### Teacher Notes

• Remind students that each problem has the same instructions at the top of the handout.
• Students can whiteboard and present their particle pictures for the equations.
• This activity is appropriate for all levels of chemistry. For additional layers of complexity, you could:
• Have students identify the type of reaction taking place in each example.
• Include the state of matter in the chemical sentences and have students consider this when drawing their particle diagrams.
• Consider having different equations at different temperatures so students must show particle movement in their diagrams as well.
• Have students write additional questions and swap with their classmates.
• Create and set up stoichiometry problems to determine limiting reactant using quantitative examples.
• An adapted version of this activity has been created as an interactive PowerPoint presentation for use during virtual instruction.

### Directions

For each word equation:

• Write a balanced chemical equation.
• Draw particulate representations of the reaction. Make sure you include the correct number of each particle based on the information provided.
• Determine which reactant is limiting and which is in excess.

1. Oxygen molecules react with hydrogen molecules to produce water molecules.

a. Write the balanced chemical equation:

b. Draw the particulate representations of the reaction if you start with three molecules of oxygen and four molecules of hydrogen:

c. Which reactant is limiting?

d. Excess?

2. Sodium atoms react with water molecules to produce sodium hydroxide and hydrogen gas.

a. Write the balanced chemical equation:

b. Draw the particulate representations of the reaction if you start with two sodium atoms and three water molecules:

c. Which reactant is limiting?

d. Excess?

3. Aluminum atoms combine with chlorine molecules to produce aluminum chloride.

a. Write the balanced chemical equation:

b. Draw the particulate representations of the reaction if you start with four aluminum atoms and three chlorine molecules:

c. Which reactant is limiting?

d. Excess?

4. Calcium atoms combine with oxygen molecules to produce calcium oxide.

a. Write the balanced Chemical equation:

b. Draw the particulate representations of the reaction if you start with six calcium atoms and four oxygen molecules:

c. Which reactant is limiting?

d. Excess?

5. Assuming the reaction below goes to completion, draw the product particles in the beaker on the right.

a. Which reactant is limiting?

b. Excess?