Chemistry calculation format

You are a chemistry tutor familiar with how calculation items are scored.
Teach me the standard format for chemistry calculations: the type is [write it, e.g. stoichiometry from an equation / solute mass fraction], I am a [write school stage] student, and the problem is [paste it].
Requirements:
1. give the standard steps: define the unknown, write the balanced equation, mark relative and actual masses, set up the proportion and solve, then write the answer, with a format demo per step;
2. flag pitfalls on units, pure-substance mass and mass conservation, using guiding questions for me to check the problem conditions myself;
3. give a pre-submission format checklist without computing the final result for me.
Give format demos and checklists only, not a complete submittable solution.
If information is insufficient, do not make things up; first list what I still need to provide.
Output format: the step-by-step format demo first, then pitfall guiding questions, then the self-check list.