Chemistry 9th Chap 13 : Topic 2 - Maryam Publications

Chemistry Chapter 13 : Topic 2

Structural Formulae

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A structural formula in organic chemistry is best described as:

A) An unambiguous representation showing how atoms are arranged and bonded in a molecule.

B) A diagram showing only the molecular mass of a compound.

C) A symbolic representation showing only the number of atoms present in a molecule.

D) A representation showing only the physical state of a substance.

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Why is a structural formula considered “unambiguous” in chemistry?

A) It gives only the empirical formula.

B) It ignores hydrogen atoms for simplicity.

C) It shows only the molecular formula without bonds.

D) It represents the exact connectivity and arrangement of atoms in a molecule.

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Which of the following correctly represents ethene as a structural formula?

A) CH₄

B) CH₃ CH₂ OH

C) CH₂=CH₂

D) CH₃ CH₃

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The structural formula CH₃ CH₂ OH represents:

A) Ethanoic acid

B) Ethanol

C) Ethane

D) Methane

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Which feature is clearly shown in a structural formula but NOT in a molecular formula?

A) Atomic masses

B) Arrangement and bonding of atoms

C) Types of elements

D) Number of atoms

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The structural formula CH₃COOCH₃ represents:

A) Ethanol

B) Methanoic acid

C) Methyl ethanoate (ester)

D) Ethane

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Which statement best explains why CH₂=CH₂ is a structural formula?

A) It shows only atomic numbers.

B) It represents ionic bonding.

C) It hides hydrogen atoms.

D) It shows the presence of a double bond between carbon atoms.

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Which of the following compounds has a functional group clearly visible in its structural formula?

A) CH₃ CH₂ OH

B) CH₄

C) H₂

D) CH₃ CH₃

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Why are structural formulas important in organic chemistry?

A) They simplify atomic masses.

B) They help determine isotopes.

C) They eliminate bonding information.

D) They distinguish between compounds with same molecular formula.

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Which of the following pairs are structural isomers based on different arrangements?

A) CH₃ CH₂ OH and CH₃ OCH₃

B) NaCl and KCl

C) H₂ and O₂

D) CH₄ and CH₂

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A molecular formula becomes more informative when converted into a structural formula because:

A) It changes chemical properties.

B) It shows bonding and arrangement of atoms.

C) It reduces number of atoms.

D) It removes hydrogen atoms.

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Which structural feature is present in CH₃COOCH₃ but absent in CH₃ CH₂ OH?

A) Carbon chain

B) Hydrogen atoms

C) Hydroxyl group

D) Ester linkage (-COO-)

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What does the double bond in CH₂=CH₂ indicate?

A) Two shared electron pairs between carbon atoms

B) Ionic bond formation

C) Hydrogen bonding

D) Single covalent bond between carbons

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Which structural formula represents a saturated compound?

A) CH≡CH

B) CH₃ CH₃

C) CH₂ CH₂ OH

D) CH₂=CH₂

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Why can two compounds have the same molecular formula but different structural formulas?

A) Because atoms can be arranged in different ways.

B) Because electrons are removed.

C) Because mass number changes.

D) Because atoms have different atomic numbers.

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Which statement about CH₂ CH₂ OH is correct?

A) It has no functional group.

B) It is an alkane.

C) It is an ester.

D) It contains hydroxyl (- OH) group.

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Which of the following best explains CH₃COOCH₃ as a structural formula?

A) It hides oxygen atoms.

B) It shows ionic bonding.

C) It represents an ester linkage between carbon atoms.

D) It shows only number of atoms.

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What is the main limitation of molecular formulas that structural formulas overcome?

A) They do not show isotopes.

B) They do not show element types.

C) They do not show arrangement of atoms.

D) They do not show atomic numbers.

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Which structural formula indicates an unsaturated hydrocarbon?

A) CH₃ CH₂ OH

B) CH₃ CH₃

C) CH₂=CH₂

D) CH₄

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Why is CH₂=CH₂ written with an equal sign (=) instead of a dash (-)?

A) To show ionic bonding

B) To show hydrogen bonding

C) To show double covalent bond

D) To show no bonding

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Which of the following best describes CH₃ CH₂ OH in terms of structure?

A) A branched hydrocarbon

B) A straight-chain alkane

C) An alcohol with hydroxyl group attached to carbon chain

D) A cyclic compound

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Which structural formula shows both carbon skeleton and functional group clearly?

A) CH₃ CH₂

B) H₂O

C) CH₄

D) CH₃ CH₂ OH

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What makes CH₃ COOCH₃ different from CH₃ CH₂ OH?

A) Physical state only

B) Number of carbon atoms

C) Type of functional group

D) Number of hydrogen atoms

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Which statement is correct about structural formulas?

A) They ignore bonding information.

B) They only show isotopes.

C) They show detailed arrangement of atoms and bonds.

D) They show only physical properties.

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Why is CH₂=CH₂ considered more informative than C₂H₄?

A) It shows molecular mass.

B) It shows density.

C) It shows bonding between carbon atoms.

D) It shows atomic number.

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