Lesson (3) - Chemistry - Senior 2

Unit 1: Chemical Calculations

Lesson 3: Mass of Product & Limiting Reactant

Instructor: Dr. Mahmoud Badr

Introduction

The lesson focuses on quantitative chemistry — understanding how to calculate the mass of a product formed in a chemical reaction using mole ratios from balanced equations, and determining the limiting reactant that governs the total yield.

Part 1: Mass of Product

This part explains how to calculate the mass of a product from known quantities of reactants using stoichiometric equations. Students learn to convert between grams, moles, and volumes of gases (at STP) to find the expected yield of a product.

• Use the molar mass to find the number of moles.
• Apply mole ratios from the balanced equation.
• Convert moles of product into grams or liters (for gases).
• Practice examples such as CO reacting with O₂ or CH₄ combustion.

Part 2: Limiting Reactant

This section introduces the concept of the limiting reactant — the substance that is completely consumed first in a reaction and limits the formation of the product.

• Identify which reactant is in excess and which is limiting.
• Calculate the amount of product formed based on the limiting reactant only.
• Apply to reactions such as methane with oxygen and the reduction of iron(III) oxide by carbon monoxide.

Summary

By mastering these calculations, students will be able to predict reaction yields accurately and understand the real-world significance of chemical equations in laboratory and industrial processes.