Organic Functional Groups & Isomers — Practice · Grade 11 Science

Chapter: Organic Chemistry & Material Design

What this practice covers

By the end of Organic Functional Groups & Isomers you should be able to:

8 questions, numeric and written answer, each with a worked explanation.

Vocabulary used: functional group, structural isomers, saturated hydrocarbon.

Problem 1

How many H atoms are in acyclic alkane C₆H…?
Hints

Write the relationship first; substitute with consistent units.

Answer and explanation

14 H atoms

2×6+2=14.

Problem 2

Why is an alcohol group not hydroxide ion?
Answer and explanation

The O–H group is covalently part of a neutral molecule, not a separate OH⁻ ion.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 3

Find hydrogen count for a simple acyclic alkane with seven carbon atoms.
Hints

List the given quantities, select a relationship, and check units before substituting.

Answer and explanation

16 H atoms

2×7+2=16.

Problem 4

What two products form in complete methane combustion?
Answer and explanation

CO₂ and H₂O; balanced CH₄+2O₂→CO₂+2H₂O.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 5

Identify the functional group in CH₃COOH. Show the reasoning, not just the conclusion.
Hints

A molecular formula alone does not specify structure.

Answer and explanation

A carboxyl group; the compound is a carboxylic acid.

Problem 6

Why can ethanol hydrogen-bond as a donor while dimethyl ether cannot donate through an O–H bond?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Ethanol contains O–H; the ether has oxygen but no O–H bond, though it can accept suitable hydrogen bonds.

Problem 7

Isomers share a formula while differing in structure or spatial arrangementIsomers share a formula while differing in structure or spatial arrangementStructural isomers: same totals, different connectionsCH₃–CH₂–OHCH₃–O–CH₃Both: C₂H₆OA molecular formula alone does not determine structure or behavior.
Original selected condensed-isomer comparison; no claim that all isomers have equally large property differences.
Interpret the supplied visual. Are the two C₂H₆O examples merely two rotations of one molecule?
Answer and explanation

No. Oxygen has different bonded neighbors, so their connectivity differs and they are structural isomers.

Structural isomers share a molecular formula but differ in connectivity, as ethanol and dimethyl ether do. Stereoisomers retain connectivity but differ in spatial arrangement. Restricted rotation or a chiral environment can make spatial differences chemically relevant; not every rotated drawing is a new stereoisomer. For alkene geometric isomerism, check whether each double-bond carbon has two different substituents before assigning a distinct arrangement. A two-dimensional formula can omit stereochemical information needed to predict behavior.

No. Oxygen has different bonded neighbors, so their connectivity differs and they are structural isomers.

Response criteria

  • Interpret labels, structures, axes, units and directions correctly.
  • Explain the chemistry relationship or mechanism.
  • Respect stated assumptions and distinguish observation from inference.

Problem 8

Two molecules are CH₃CH₂OH and CH₃OCH₃. Show their shared molecular formula, identify their structural-isomer relationship and distinguish their hydrogen-bond donor roles.
Answer and explanation

Both are C₂H₆O but have different connectivity, so they are structural isomers. Ethanol has an O–H donor; dimethyl ether lacks O–H and does not supply that donor pattern, although its oxygen can accept suitable interactions.

Both are C₂H₆O but have different connectivity, so they are structural isomers. Ethanol has an O–H donor; dimethyl ether lacks O–H and does not supply that donor pattern, although its oxygen can accept suitable interactions.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the chemical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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