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Comparing Molecular Representations 4 questions

Comparing Molecular Representations

New Regents original practice • Name: ____________________ Date: __________ Show your work for written answers.

A molecular formula gives the kinds and numbers of atoms. A structural representation also shows which atoms are bonded.

Question 1

What information is given directly by the molecular formula C₂H₆O?

  1. The positions of all atoms in space
  2. Two C atoms, six H atoms, and one O atom per molecule
  3. A bond angle of exactly 90°
  4. The identity of every pair of bonded atoms

Question 2

Explain what the lines in H–O–H show that the molecular formula H₂O does not show by itself.

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Question 3

Which representation explicitly shows both oxygen atoms bonded to the same carbon atom?

  1. CO₂ alone
  2. 2CO₂
  3. O=C=O
  4. C + O₂ without a structure

Question 4

A flat structural diagram shows the correct connections in a molecule. Explain why it may be insufficient to determine the molecule’s three-dimensional shape.

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Two Models with the Same Atom Counts 4 questions

Two Models with the Same Atom Counts

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The diagrams show which atoms are joined in two molecular models. A line represents a single covalent bond. Count all of the labeled atoms in each panel.

Model A has a C–C–O chain. Three H atoms attach to the first C, two H attach to the second C, and one H attaches to O. Model B has a C–O–C chain with three H atoms attached to each C.
Two different arrangements of carbon, hydrogen, and oxygen atoms.
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Question 5

Which molecular formula matches both models?

  1. CH₃O
  2. C₂H₆O
  3. C₂H₄O
  4. C₃H₆O

Question 6

Which model contains an O–H bond? Explain using the connections in the diagram.

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Question 7

How many hydrogen atoms are attached directly to oxygen in model B?

  1. 0
  2. 1
  3. 2
  4. 3

Question 8

Explain why the shared molecular formula is insufficient to decide which model shows the C–O–C connection.

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