Introduction:
In class 10, students learn about decomposition reactions where a single compound breaks down into two or more simpler substances. These reactions are often influenced by various factors, including the presence of catalysts. Catalysts are substances that speed up the rate of a chemical reaction without being consumed in the process. However, if a student forgets to mention the catalyst, such as light or electricity, in a decomposition reaction, it may lead to a deduction of marks.

Explanation:
The inclusion of catalysts in decomposition reactions is crucial because they play a significant role in facilitating the reaction. Here's a detailed explanation of the potential deduction of marks for forgetting to mention the catalyst:

1. Lack of completeness: By omitting the catalyst in a decomposition reaction, the student fails to provide a complete and accurate representation of the reaction. This omission could indicate a lack of understanding or attention to detail, which may result in a deduction of marks.

2. Understanding the role of catalysts: Mentioning catalysts like light or electricity in a decomposition reaction demonstrates the student's understanding of how catalysts affect the reaction rate. It showcases their knowledge of the specific conditions required for the reaction to occur. By overlooking this aspect, the student may lose marks related to the understanding and application of concepts.

3. Linking catalysts to reaction rate: Catalysts, such as light or electricity, can significantly influence the reaction rate in a decomposition reaction. Light energy can provide the necessary activation energy to initiate the reaction, while electricity can facilitate the movement of ions and accelerate the process. By not mentioning these catalysts, the student fails to establish a connection between the catalyst and the reaction rate, resulting in a potential loss of marks.

4. Impact on overall understanding: Forgetting to mention catalysts can indicate a gap in the student's overall understanding of decomposition reactions. It suggests that they may not be able to explain the factors influencing reaction rates comprehensively. Consequently, the examiner may deduct marks related to conceptual understanding and the ability to apply knowledge.

Conclusion:
In conclusion, it is essential for students to mention catalysts such as light or electricity when writing decomposition reactions in class 10. Forgetting to include these catalysts may result in a deduction of marks due to the lack of completeness, inadequate understanding of catalysts' role, failure to link catalysts to reaction rates, and an overall impact on the student's understanding. Therefore, it is crucial to pay attention to all the components of a reaction to ensure a comprehensive and accurate representation, leading to better performance in examinations.

No marks will be deducted if not mentionedOn the arrowbut it must be mentioned earlier