Chemistry 9th Chap 6 : Topic 3 - Maryam Publications

Chemistry Chapter 6 : Topic 3

Empirical Formula

1 / 20

Which statement best defines the empirical formula of a compound?

A) It gives the molecular mass of a compound in grams.

B) It represents the exact number of atoms of each element in a molecule.

C) It shows the simplest whole number ratio of atoms of different elements in a compound.

D) It indicates the structural arrangement of atoms in a molecule.

2 / 20

A compound has molecular formula C₂H₄. What is its empirical formula?

A) C₂H₄

B) CH₂

C) CH₄

D) C₄H₈

3 / 20

Which of the following compounds has the same empirical and molecular formula?

A) CO₂

B) C₆H₁₂O₆

C) H₂O₂

D) C₂H₆

4 / 20

Why is the empirical formula always expressed in whole numbers?

A) Because fractions of atoms cannot exist in a compound.

B) Because chemical reactions require whole numbers.

C) Because molecular mass must be an integer.

D) Because atoms combine only in decimal ratios.

5 / 20

A compound contains 40% carbon, 6.67% hydrogen, and 53.33% oxygen. What is its empirical formula?

A) C₃H₆O₃

B) C₂H₄O₂

C) CH₂O

D) CHO

6 / 20

Which statement correctly distinguishes empirical formula from molecular formula?

A) Empirical formula shows simplest ratio; molecular shows actual number of atoms.

B) Molecular formula is always simpler than empirical formula.

C) Empirical formula shows actual number of atoms; molecular shows ratio.

D) Both always represent the same thing.

7 / 20

The empirical formula of a compound is CH₂. Which of the following could be its molecular formula?

A) C₂H₄

B) C₃H₆

C) CH₂

D) All of these

8 / 20

Which compound cannot be simplified to a simpler empirical formula?

A) C₄H₈

B) C₂H₆

C) N₂O₄

D) NH₃

9 / 20

What is the empirical formula of C₆H₁₂O₆?

A) C₂H₄O₂

B) C₃H₆O₃

C) CH₂O

D) All of these

10 / 20

Which of the following best explains why empirical formula is important?

A) It gives the simplest ratio for understanding composition.

B) It determines the color of a compound.

C) It shows the shape of molecules.

D) It indicates physical state.

11 / 20

A compound has the empirical formula HO. Its molecular mass is twice the empirical formula mass. What is the molecular formula?

A) H₄O₂

B) HO

C) H₂O

D) H₂O₂

12 / 20

Which step is essential when determining an empirical formula from experimental data?

A) Measuring density

B) Determining color

C) Calculating boiling point

D) Converting masses into moles

13 / 20

If the mole ratio of elements in a compound is 1.5 : 3, what should be done to find empirical formula?

A) Divide by 3

B) Multiply all ratios to convert into whole numbers

C) Use as it is

D) Ignore decimal values

14 / 20

A compound contains nitrogen and oxygen in the ratio 1 :2. What is its empirical formula?

A) NO₂

B) NO

C) N₂O₄

D) N₂O

15 / 20

Which of the following statements is incorrect about empirical formula?

A) It may not represent actual number of atoms.

B) It gives simplest ratio of atoms.

C) It is always same as molecular formula.

D) It is derived from experimental data.

16 / 20

If the empirical formula is CH and molecular mass is 78, what is the molecular formula?

A) C₃H₃

B) C₂H₂

C) CH

D) C₆H₆

17 / 20

Which situation would result in identical empirical and molecular formulas?

A) When molecular mass is high.

B) When compound contains oxygen.

C) When ratio is already simplest.

D) When ratio is reducible.

18 / 20

What is the empirical formula of a compound containing 2 moles of carbon and 6 moles of hydrogen?

A) CH₂

B) C₂H₆

C) C₃H₆

D) CH₃

19 / 20

Which method is used to determine empirical formula experimentally?

A) Electrical conductivity

B) Percentage composition analysis

C) Spectroscopy only

D) Boiling point determination

20 / 20

Why is dividing by the smallest mole value important in empirical formula calculation?

A) To obtain simplest ratio

B) To make numbers larger

C) To avoid decimals

D) To find molecular mass

Your score is

0%