Empirical & Molecular Formula
Authored by Patricia Dimapilis
Chemistry
10th - 12th Grade
NGSS covered
Used 1K+ times
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About
This quiz focuses on empirical and molecular formulas, a fundamental topic in stoichiometry and chemical composition analysis appropriate for grades 10-12 chemistry. Students must demonstrate mastery of several interconnected concepts: converting percent composition data to empirical formulas using molar masses and mole ratios, calculating molecular formulas from empirical formulas when given molecular mass, determining percent composition from molecular formulas, and distinguishing between empirical and molecular representations of compounds. The problems require students to perform multi-step calculations involving atomic masses, mole conversions, ratio simplification, and multiplicative relationships between empirical and molecular formulas. Students need solid computational skills, understanding of significant figures, and the ability to recognize when empirical and molecular formulas are identical versus when they differ by whole-number multiples. Created by Patricia Dimapilis, a Chemistry teacher in the US who teaches grades 10 and 12. This quiz serves as an excellent tool for formative assessment or guided practice as students build proficiency with formula determination problems. Teachers can use these questions as warm-up problems to activate prior knowledge about molar mass calculations, assign them as homework to reinforce classroom instruction, or implement them during review sessions before unit tests. The variety of question types—from computational problems requiring percent composition analysis to conceptual questions about the relationship between empirical and molecular formulas—allows instructors to gauge both procedural fluency and conceptual understanding. This assessment aligns with NGSS HS-PS1-7 (using mathematical representations to support the claim that atoms are conserved during chemical reactions) and supports Common Core mathematical practices in chemistry contexts.
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12 questions
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1.
MULTIPLE CHOICE QUESTION
15 mins • 12 pts
Glycerol has a molar mass of 92.09g/mol. Its percent composition is: 39.12% C, 8.75% H, and 51.12% O. What is the molecular formula for glycerol?
2.
MULTIPLE CHOICE QUESTION
15 mins • 12 pts
What is the empirical formula for the following molecular formula: C6H14
3.
MULTIPLE CHOICE QUESTION
1 min • 12 pts
What is the molecular formula if the empirical formula is C2H5 and the molecular molar mass is 58.14 g/mol?
4.
MULTIPLE CHOICE QUESTION
15 mins • 12 pts
What is the empirical formula for the following molecular formula: C5H12
5.
MULTIPLE CHOICE QUESTION
1 min • 12 pts
Find the percent composition of N2S2.
Tags
NGSS.HS-PS1-7
6.
MULTIPLE CHOICE QUESTION
15 mins • 12 pts
What is the molecular formula for a compound with the empirical formula: K2SO4 and a molecular mass of 696g.
7.
MULTIPLE CHOICE QUESTION
15 mins • 12 pts
What is the molecular formula for a compound with the empirical formula: CaCl2 and a molecular mass of 330g.
Tags
NGSS.HS-PS1-7
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