Chemistry 9th Chap 13 : Topic 3 - Maryam Publications

Chemistry Chapter 13 : Topic 3

Drawing Structural Formulae

1 / 20

Which statement best describes a structural formula of a molecule?

A) It shows only the molecular mass of a compound.

B) It shows the exact arrangement of atoms and bonds in a molecule.

C) It represents ions present in a compound.

D) It shows only the number of atoms of each element.

2 / 20

Why is the structural formula of methane (CH₄) written with four single bonds around carbon?

A) Carbon has four valence electrons and forms four covalent bonds.

B) Methane contains four carbon atoms.

C) Carbon has four protons available for bonding.

D) Hydrogen forces carbon to form four ionic bonds.

3 / 20

Which of the following correctly represents the structural idea of water (H₂O)?

A) H-H-O arrangement

B) O-O-H structure

C) H=O=H with double bonds

D) H-O-H with two single bonds

4 / 20

What is the main advantage of structural formula over molecular formula?

A) It shows bonding and arrangement of atoms.

B) It shows isotopes present.

C) It shows only atomic masses.

D) It shows physical state of matter.

5 / 20

Which structural feature is correct for oxygen gas (O₂)?

A) O-O-O chain

B) O=O double bond

C) O-O single bond

D) O≡O triple bond

6 / 20

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

A) Because their mass is different.

B) Because they contain different elements.

C) Because atoms are randomly arranged.

D) Because bonding arrangement can differ (isomerism).

7 / 20

Which structural formula correctly represents carbon dioxide (CO₂)?

A) C-O-O with triple bonds

B) O-C-O with single bonds

C) O-O-C structure

D) O=C=O with double bonds

8 / 20

What does a line in structural formula represent?

A) Atomic number difference

B) A proton transfer

C) A nucleus

D) A pair of shared electrons (covalent bond)

9 / 20

Which statement is true about structural formula of ethane (C₂H₆)?

A) Carbon atoms are triple bonded.

B) It contains ionic bonding.

C) Each carbon forms four single bonds.

D) Hydrogen forms double bonds with carbon.

10 / 20

Why is ammonia (NH₃) drawn with a lone pair on nitrogen?

A) Nitrogen has no valence electrons.

B) Nitrogen completes octet with three bonds and one lone pair.

C) Hydrogen forces lone pairs.

D) It is an ionic compound.

11 / 20

Which structural change correctly converts molecular formula to structural formula of HCl?

A) H-H-Cl

B) H-Cl (single bond)

C) H=Cl (double bond)

D) Cl-Cl-H

12 / 20

What is the structural representation of nitrogen gas (N₂)?

A) N≡N

B) N-N

C) N-N-N

D) N=N

13 / 20

Why is structural formula important in organic chemistry?

A) It gives atomic weights.

B) It helps calculate density.

C) It shows nuclear structure.

D) It shows bonding and functional groups.

14 / 20

Which of the following is a correct structural difference between CO and CO₂?

A) CO₂ has one single bond.

B) CO has a triple bond, CO₂ has two double bonds.

C) CO₂ has two double bonds.

D) Both have identical bonding.

15 / 20

What does structural formula of methane (CH₄) emphasize most?

A) Mass number of carbon

B) Arrangement of hydrogen atoms around carbon

C) Physical state

D) Presence of isotopes

16 / 20

Why are structural formulas necessary for distinguishing isomers?

A) Because isomers differ in mass.

B) Because they have different atoms.

C) Because they are ionic compounds.

D) Because they have same molecular formula but different arrangements.

17 / 20

Which of the following correctly shows bonding in ethene (C₂H₄)?

A) C≡C triple bond

B) C-C single bond only

C) C=C double bond

D) C-C-C chain

18 / 20

What is the structural significance of a double bond?

A) Sharing of two electron pairs

B) Transfer of electrons

C) No bonding electrons

D) Sharing of one electron pair

19 / 20

Which structural formula correctly represents hydrogen peroxide (H₂O₂)?

A) O=O-H₂

B) H-H-O-O

C) H-O=O-H

D) H-O-O-H

20 / 20

What is the main limitation of molecular formula compared to structural formula?

A) It cannot show element types.

B) It cannot show bonding arrangement.

C) It cannot show mass.

D) It cannot show number of atoms.

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