Chemistry 9th Chap 6 : Topic 2 - Maryam Publications

Chemistry Chapter 6 : Topic 2

Molecular Formula

1 / 20

Which statement best explains the meaning of a molecular formula of a compound?

A) It represents the simplest whole-number ratio of atoms present in a compound.

B) It indicates only the types of elements present without specifying their numbers.

C) It describes the arrangement of atoms in a crystal lattice.

D) It shows the exact number and kinds of atoms present in one molecule of a compound.

2 / 20

Which of the following correctly distinguishes between molecular formula and empirical formula?

A) Molecular formula shows actual composition, empirical formula shows simplest ratio.

B) Both formulas always represent identical information for all compounds.

C) Molecular formula shows simplest ratio, empirical formula shows actual number of atoms.

D) Empirical formula applies only to ionic compounds while molecular formula applies to covalent compounds.

3 / 20

The molecular formula of hydrogen peroxide is H₂O₂. What information does this provide?

A) There are two hydrogen atoms and two oxygen atoms in one molecule.

B) The compound contains four atoms but their types are not specified.

C) Hydrogen and oxygen combine in the simplest ratio of 1 :1.

D) Hydrogen and oxygen are present in equal masses.

4 / 20

Which of the following compounds has a molecular formula that is NOT the same as its empirical formula?

A) CO₂

B) H₂O

C) C₂H₄

D) NH₃

5 / 20

A compound has a molecular formula C₆H₁₂O₆. What does the subscript ‘6’ with carbon indicate?

A) Six carbon atoms are present in one molecule.

B) Carbon contributes six electrons.

C) There are six molecules of carbon.

D) Carbon has a valency of six.

6 / 20

Which of the following statements is correct regarding molecular formula representation?

A) It represents the structure and bonding between atoms.

B) It always shows the simplest ratio of atoms.

C) It gives exact atomic composition of a molecule.

D) It only applies to ionic compounds.

7 / 20

Which situation best describes the importance of molecular formula?

A) Identifying the exact number of atoms in a molecule

B) Measuring boiling point

C) Predicting physical state only

D) Determining the color of a compound

8 / 20

The molecular formula of a compound is N₂O₄. Which conclusion can be drawn?

A) Nitrogen and oxygen are present in equal proportion.

B) It cannot be simplified.

C) The molecule contains 2 nitrogen and 4 oxygen atoms.

D) The simplest ratio of atoms is 2 :4.

9 / 20

Which of the following is true for all molecular formulas?

A) They show exact number of atoms in one molecule.

B) They show arrangement of atoms in space.

C) They always match empirical formulas.

D) They always represent ionic compounds.

10 / 20

If a compound has molecular formula C₃H₆, what can be inferred?

A) It must have three carbon atoms and six hydrogen atoms in one molecule.

B) It is the simplest representation of the compound.

C) It is an ionic compound.

D) It contains only one carbon atom.

11 / 20

Which of the following best explains why molecular formulas are important in chemistry?

A) They describe bonding angles.

B) They provide exact atomic composition of compounds.

C) They help in identifying physical properties only.

D) They indicate only types of atoms.

12 / 20

A student says that molecular formula of a compound gives only the types of atoms present. Why is this statement incorrect?

A) Because it also gives number of atoms of each element.

B) Because it shows arrangement of atoms.

C) Because it shows physical state.

D) Because it also gives mass of atoms.

13 / 20

Which compound has a molecular formula indicating equal number of atoms of each element?

A) CO₂

B) H₂O₂

C) H₂O

D) NH₃

14 / 20

What is the main limitation of a molecular formula?

A) It does not show the number of atoms.

B) It applies only to metals.

C) It does not show types of atoms.

D) It does not indicate how atoms are arranged or bonded.

15 / 20

Which statement correctly compares H₂O and H₂O₂ based on their molecular formulas?

A) They differ in number of oxygen atoms.

B) Both have same types and numbers of atoms.

C) Both have same number of atoms.

D) They have identical properties.

16 / 20

Why can molecular formula be considered more informative than empirical formula?

A) It gives exact atomic composition.

B) It shows simplest ratio.

C) It shows chemical reactions.

D) It indicates physical state.

17 / 20

Which of the following represents a molecular formula?

A) CO₂

B) CH

C) CaO

D) NaCl

18 / 20

A compound has empirical formula CH₂ and molecular mass twice that of empirical formula. What is molecular formula?

A) CH₂

B) CH₄

C) C₃H₆

D) C₂H₄

19 / 20

Which statement is incorrect about molecular formulas?

A) They show exact number of atoms.

B) They indicate types of elements.

C) They always show simplest ratio.

D) They are used for covalent compounds.

20 / 20

Which of the following best reflects the concept of “one molecule” in molecular formula?

A) A large collection of atoms.

B) A mixture of different compounds.

C) A random group of elements.

D) The smallest unit of a compound showing its composition.

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