I think because students get confused or forget which elements are diatomic A decomposition usually is simple and straight forward but many students just don't know which elements should be diatomic and which shouldn't.
Common mistakes in decomposition reactions include confusion about diatomic elements, overlooking energy requirements, misidentifying reaction types, neglecting product states, and skipping balanced equations. Recognizing these errors can aid students in improving their understanding and performance in chemistry. A good practice is to ensure they balance chemical equations and double-check the states of products.
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