A Level Chemistry OCR Practice Exam

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Prepare for the A Level Chemistry OCR Exam with quizzes. Study with flashcards, multiple choice questions, hints, and explanations. Enhance your understanding and boost your confidence for success!

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Which scenario best illustrates the characterization of an empirical formula?

C6H12O6 is an empirical formula for glucose
CH2 is an empirical formula for ethylene
NaCl is an empirical formula for table salt
C3H8 is an empirical formula for propane

The correct answer is: CH2 is an empirical formula for ethylene

The characterization of an empirical formula refers to the simplest whole-number ratio of the elements in a compound. In this context, CH2 is indeed an empirical formula for ethylene, as it represents the simplest ratio of carbon to hydrogen in that compound. Ethylene’s molecular formula is C2H4, which can be simplified to the empirical formula CH2 by dividing both subscripts by 2. An empirical formula gives a basic understanding of the composition of a substance, without revealing the actual number of atoms in the molecule. In contrast, glucose (C6H12O6) and propane (C3H8) both have molecular formulas that cannot be expressed in simpler whole-number ratios without losing information about the actual composition, as they are already in their simplest ratio specific to their unique molecular structure. While NaCl is a correct representation of a substance's empirical formula, it is also the molecular formula for sodium chloride, hence it doesn't demonstrate the concept as clearly as option B does.