Reacting Masses

This lesson teaches you how to use a balanced chemical equation to calculate the masses of reactants and products involved in a reaction. These reacting mass calculations are among the most common quantitative questions in GCSE Chemistry exams and are required by the Edexcel specification (1CH0).

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The Step-by-Step Method

Every reacting mass calculation follows the same systematic method. Learn this method and you can tackle any question.

flowchart TD
    A["Step 1: Write the balanced equation"] --> B["Step 2: Calculate Mr of each relevant substance"]
    B --> C["Step 3: Find the moles of the substance you know"]
    C --> D["Step 4: Use the molar ratio from the equation"]
    D --> E["Step 5: Calculate the mass of the substance you want"]
    style A fill:#e6f3ff,stroke:#333
    style B fill:#e6f3ff,stroke:#333
    style C fill:#e6f3ff,stroke:#333
    style D fill:#e6f3ff,stroke:#333
    style E fill:#e6f3ff,stroke:#333

The Method in Detail