Chemistry 9th Chap 6 : Topic 1 - Maryam Publications

Chemistry Chapter 6 : Topic 1

Common Chemical Formulae

1 / 25

Which statement correctly explains why oxygen exists as O₂ rather than O in its natural state?

A) Oxygen atoms repel each other due to similar charges and remain separate.

B) Oxygen atoms cannot share electrons with each other.

C) Oxygen atoms are unstable individually and combine to achieve a stable electronic configuration.

D) Oxygen forms O₂ only under high pressure conditions.

2 / 25

Which of the following pairs correctly represents the formulae of elemental gases present in air?

A) N, O₂

B) N₂, O₂

C) N₂, O

D) N, O

3 / 25

Which compound has a formula that reflects a 2 :1 ratio of hydrogen to oxygen atoms?

A) HO₂

B) H₂O

C) H₂O₂

D) H₃O

4 / 25

Which of the following formulas represents a compound formed by ionic bonding between sodium and chlorine?

A) NaCl

B) Na₂Cl₂

C) Na₂Cl

D) NaCl₂

5 / 25

Which statement best justifies the formula CO₂ for carbon dioxide?

A) Oxygen requires two electrons to complete its valence shell, leading to two oxygen atoms bonding with one carbon.

B) Oxygen atoms do not share electrons.

C) Carbon donates electrons to oxygen atoms.

D) Carbon can only form single bonds.

6 / 25

Which of the following is the correct formula of ammonia and why?

A) NH, because nitrogen needs only one hydrogen

B) NH₄, because nitrogen accepts four electrons

C) NH₃, because nitrogen completes its octet by bonding with three hydrogen atoms

D) NH₂, because nitrogen forms two bonds

7 / 25

Which formula represents a molecule that contains a peroxide linkage?

A) H₂O

B) CO₂

C) H₂O₂

D) CH₄

8 / 25

Which of the following correctly represents the molecular formula of methane based on carbon’s valency?

A) CH₄

B) CH₂

C) C₂H₄

D) CH₃

9 / 25

Which formula represents a compound where calcium combines with chlorine ions?

A) Ca₂Cl₂

B) CaCl₂

C) Ca₂Cl

D) CaCl

10 / 25

Which of the following formulas correctly represents sulfur in its most stable elemental form?

A) S₈

B) S₄

C) S

D) S₂

11 / 25

Which of the following compounds has equal numbers of carbon and oxygen atoms?

A) C₂O₃

B) C₂O

C) CO₂

D) CO

12 / 25

Which formula represents a compound formed by magnesium and oxygen?

A) MgO₂

B) MgO

C) Mg₂O

D) Mg₂O₂

13 / 25

Which statement correctly explains the formula HCl?

A) Hydrogen and chlorine share one pair of electrons forming a covalent bond.

B) Chlorine donates electrons to hydrogen.

C) Hydrogen forms ionic bonds only.

D) Hydrogen transfers electrons to chlorine.

14 / 25

Which of the following formulas represents a compound with a polyatomic ion?

A) CaCO₃

B) CO₂

C) NaCl

D) H₂O

15 / 25

Which formula correctly represents glucose?

A) CH₂O

B) C₁₂H₂₂O₁₁

C) C₆H₆O₆

D) C₆H₁₂O₆

16 / 25

Which formula represents a compound with two hydrogen atoms bonded to one sulfur atom?

A) HS

B) H₂SO₄

C) H₂S

D) HS₂

17 / 25

Which compound’s formula indicates that it contains more oxygen atoms than hydrogen atoms?

A) CO₂

B) H₂O

C) CH₄

D) H₂O₂

18 / 25

Which of the following correctly represents the formula of sodium hydroxide?

A) Na₂OH

B) NaH₂O

C) NaO

D) NaOH

19 / 25

Which of the following best explains why nitrogen forms N₂ instead of N₄?

A) Triple bonding between two nitrogen atoms provides maximum stability.

B) Nitrogen prefers ionic bonding.

C) Nitrogen atoms cannot bond with more than one atom.

D) Nitrogen atoms repel each other strongly.

20 / 25

Which statement best explains the formula NH₃ in terms of valency?

A) Hydrogen has valency 2.

B) Hydrogen has valency 3.

C) Nitrogen has valency 5.

D) Nitrogen has valency 3.

21 / 25

Which formula represents a compound formed by aluminum and oxygen?

A) AlO₂

B) Al₂O₃

C) Al₃O₂

D) AlO

22 / 25

Which of the following formulas represents a compound with a 1 :2 ratio of metal to non-metal atoms?

A) MgO

B) NaCl

C) Al₂O₃

D) CaCl₂

23 / 25

Which compound has the simplest whole number ratio of atoms identical to CH₂O?

A) C₃H₆O₃

B) CH₄O

C) C₆H₁₂O₆

D) C₂H₄O₂

24 / 25

Which of the following correctly represents the formula of carbon monoxide?

A) C₂O₂

B) C₂O

C) CO₂

D) CO

25 / 25

Which formula represents a compound where hydrogen is bonded to a halogen?

A) HCl

B) NH₃

C) H₂O

D) CH₄

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