Percent Composition, Empirical & Molecular Formulas — Drills · Grade 11 Science
Chapter: Reactions, Moles & CompositionWhat these drills covers
By the end of Percent Composition, Empirical & Molecular Formulas you should be able to:
- I can convert mass composition to a simplest mole ratio.
- I can use molar mass to distinguish empirical and molecular formulas.
2 questions, numeric and written answer, each with a worked explanation.
Vocabulary used: empirical formula, molecular formula, percent composition.
Problem 1
With C=12 and O=16, find percent carbon in CO₂.
Hints
Write the relationship first; substitute with consistent units.
Answer and explanation
27.27 %
12/44 ×100 = 27.27%.
Problem 2
Why not use mass ratios directly as formula subscripts?
Answer and explanation
Subscripts count atoms; convert mass to moles because elements have different atomic masses.
Response criteria
- State a scientifically accurate conclusion.
- Show the calculation or mechanism that supports it.
- Include units, conditions, or limits where relevant.