Mole Concept and Molecular Mass MCQ Quiz - Objective Question with Answer for Mole Concept and Molecular Mass - Download Free PDF

Last updated on May 29, 2025

Latest Mole Concept and Molecular Mass MCQ Objective Questions

Mole Concept and Molecular Mass Question 1:

The highest number of atoms is present in

  1. 0.40g Ca
  2. 12 g He
  3. 4 g He
  4. 46 g Na

Answer (Detailed Solution Below)

Option 2 : 12 g He

Mole Concept and Molecular Mass Question 1 Detailed Solution

CONCEPT:

Number of Atoms and Moles

  • The number of atoms in a given sample can be calculated using the concept of moles and Avogadro's number (6.022 × 1023 atoms per mole).
  • Moles of a substance can be calculated using the formula:

    Moles = Mass of the substance (in grams) / Molar mass (in g/mol)

  • The total number of atoms is then given by:

    Number of Atoms = Moles × Avogadro's number

EXPLANATION

1) 0.40 g Ca:

  • Molar mass of Ca = 40 g/mol
  • Moles of Ca = 0.40 g / 40 g/mol = 0.01 mol
  • Number of Atoms = 0.01 mol × 6.022 × 1023 = 6.022 × 1021

2) 12 g He:

  • Molar mass of He = 4 g/mol
  • Moles of He = 12 g / 4 g/mol = 3 mol
  • Number of Atoms = 3 mol × 6.022 × 1023 = 1.8066 × 1024

3) 4 g He:

  • Molar mass of He = 4 g/mol
  • Moles of He = 4 g / 4 g/mol = 1 mol
  • Number of Atoms = 1 mol × 6.022 × 1023 = 6.022 × 1023

4) 46 g Na:

  • Molar mass of Na = 23 g/mol
  • Moles of Na = 46 g / 23 g/mol = 2 mol
  • Number of Atoms = 2 mol × 6.022 × 1023 = 1.2044 × 1024

Comparing the number of atoms: The highest number of atoms is in 12 g He.

Therefore, the answer is 12 g He.

Mole Concept and Molecular Mass Question 2:

The mass of 0:5 mole of N2 gas is 

  1. 7 g
  2. 14 g
  3. 21 g
  4. 28 g

Answer (Detailed Solution Below)

Option 2 : 14 g

Mole Concept and Molecular Mass Question 2 Detailed Solution

CONCEPT:

Molar Mass and Mole Calculation

  • The molar mass of a substance is the mass of one mole of that substance, usually expressed in grams per mole (g/mol).
  • The molar mass of nitrogen gas (N2) can be calculated by adding the atomic masses of two nitrogen atoms.
  • The molar mass of a single nitrogen atom (N) is approximately 14 g/mol.

EXPLANATION:

  • For nitrogen gas (N2):
    • The molar mass of N2 = 14 g/mol (for one N atom) × 2 = 28 g/mol
  • To find the mass of 0.5 mole of N2 gas, we use the formula:
    • Mass = Number of moles × Molar mass
    • Mass = 0.5 moles × 28 g/mol
    • Mass = 14 grams

Therefore, the mass of 0.5 mole of N2 gas is 14 grams.

Mole Concept and Molecular Mass Question 3:

The volume of one mole of a gas at normal temperature and pressure is _________ Litre.

  1. 11.2
  2. 22.4
  3. 33.3 
  4. 44.4

Answer (Detailed Solution Below)

Option 2 : 22.4

Mole Concept and Molecular Mass Question 3 Detailed Solution

The correct answer is Option 2.

Key Points

  • One mole of an ideal gas occupies 22.4 liters at standard temperature and pressure (STP).
  • Standard temperature and pressure (STP) is defined as a temperature of 0°C (273.15 K) and a pressure of 1 atm (101.325 kPa).
  • This volume is known as the molar volume of a gas.
  • The concept is based on the Ideal Gas Law, which states that PV=nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is temperature.

Additional Information

  • Avogadro's Law: This law states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules.
  • Ideal Gas Law: The equation PV=nRT is used to describe the behavior of an ideal gas.
  • Gas Constant (R): The value of R in the Ideal Gas Law is 8.314 J/(mol·K) or 0.0821 L·atm/(mol·K).
  • Real Gases: Deviations from the Ideal Gas Law occur at high pressures and low temperatures where intermolecular forces become significant.
  • Molar Mass: The mass of one mole of a substance (element or compound) is expressed in grams per mole (g/mol).

Mole Concept and Molecular Mass Question 4:

How many moles of CO2 are present in a gas jar containing 1.506 × 1023 molecules of carbon dioxide? 

  1. 0.5
  2. 1
  3. 2
  4. 0.25

Answer (Detailed Solution Below)

Option 4 : 0.25

Mole Concept and Molecular Mass Question 4 Detailed Solution

The correct answer is 0.25

Concept:

Mole:

  • The mole is a unit of measurement for the amount of substance.
  • One mole of any substance contains exactly \(6.022 \times 10^{23}\) entities (this number is known as Avogadro's number \(N_A\).
  • Formula to calculate moles: \(n = \frac{N}{N_A}\)

Calculation:

Given,

Number of molecules of\( CO_2 = N = 1.506 \times 10^{23}\)

Avogadro's number, \(N_A = 6.022 \times 10^{23} \, \text{molecules/mol}\)

Number of moles of \(CO_2\),

\(n = \frac{N}{N_A}\)

\( n = \frac{1.506 \times 10^{23}}{6.022 \times 10^{23}}\)

⇒ \(n \approx 0.25 \ moles\)

∴ The number of moles of \( CO_2 \) present is 0.25.

Mole Concept and Molecular Mass Question 5:

In a compound having molecular formula XY, element 'X' belongs to the 3rd period and the 2nd group, whereas, element 'Y' belongs to the 2nd period and the 16th group. What is the relative molecular mass of the compound XY?

  1. 40u
  2. 35u
  3. 64u
  4. 50u

Answer (Detailed Solution Below)

Option 1 : 40u

Mole Concept and Molecular Mass Question 5 Detailed Solution

The correct answer is 40u.

Key Points

  • Element 'X' belongs to the 3rd period and the 2nd group of the periodic table, which identifies it as Magnesium (Mg) with an atomic mass of 24u.
  • Element 'Y' belongs to the 2nd period and the 16th group of the periodic table, which identifies it as Oxygen (O) with an atomic mass of 16u.
  • The molecular formula XY indicates a 1:1 ratio of Magnesium to Oxygen in the compound.
  • The relative molecular mass is calculated as the sum of the atomic masses of X and Y: 24u (Mg) + 16u (O) = 40u.

Additional Information

  • Periodic Table:
    • The periodic table is a tabular arrangement of chemical elements, organized by their atomic number, electron configuration, and recurring chemical properties.
    • Elements are arranged in rows called periods and columns called groups.
  • Magnesium (Mg):
    • Magnesium is a chemical element with the symbol Mg and atomic number 12.
    • It is a shiny gray solid, often used in alloys and as a reducing agent in the production of metals.
  • Oxygen (O):
    • Oxygen is a chemical element with the symbol O and atomic number 8.
    • It is a highly reactive nonmetal and an oxidizing agent that readily forms oxides with most elements and compounds.
  • Relative Molecular Mass:
    • The relative molecular mass (molecular weight) of a molecule is the sum of the atomic masses of all the atoms in the molecule.
    • It is calculated using the atomic masses of the constituent elements as given in the periodic table.

Top Mole Concept and Molecular Mass MCQ Objective Questions

How many moles of CO2 are present in a gas jar containing 1.506 × 1023 molecules of carbon dioxide? 

  1. 0.5
  2. 1
  3. 2
  4. 0.25

Answer (Detailed Solution Below)

Option 4 : 0.25

Mole Concept and Molecular Mass Question 6 Detailed Solution

Download Solution PDF

The correct answer is 0.25

Concept:

Mole:

  • The mole is a unit of measurement for the amount of substance.
  • One mole of any substance contains exactly \(6.022 \times 10^{23}\) entities (this number is known as Avogadro's number \(N_A\).
  • Formula to calculate moles: \(n = \frac{N}{N_A}\)

Calculation:

Given,

Number of molecules of\( CO_2 = N = 1.506 \times 10^{23}\)

Avogadro's number, \(N_A = 6.022 \times 10^{23} \, \text{molecules/mol}\)

Number of moles of \(CO_2\),

\(n = \frac{N}{N_A}\)

\( n = \frac{1.506 \times 10^{23}}{6.022 \times 10^{23}}\)

⇒ \(n \approx 0.25 \ moles\)

∴ The number of moles of \( CO_2 \) present is 0.25.

The mass of 0:5 mole of N2 gas is 

  1. 7 g
  2. 14 g
  3. 21 g
  4. 28 g

Answer (Detailed Solution Below)

Option 2 : 14 g

Mole Concept and Molecular Mass Question 7 Detailed Solution

Download Solution PDF

CONCEPT:

Molar Mass and Mole Calculation

  • The molar mass of a substance is the mass of one mole of that substance, usually expressed in grams per mole (g/mol).
  • The molar mass of nitrogen gas (N2) can be calculated by adding the atomic masses of two nitrogen atoms.
  • The molar mass of a single nitrogen atom (N) is approximately 14 g/mol.

EXPLANATION:

  • For nitrogen gas (N2):
    • The molar mass of N2 = 14 g/mol (for one N atom) × 2 = 28 g/mol
  • To find the mass of 0.5 mole of N2 gas, we use the formula:
    • Mass = Number of moles × Molar mass
    • Mass = 0.5 moles × 28 g/mol
    • Mass = 14 grams

Therefore, the mass of 0.5 mole of N2 gas is 14 grams.

The volume of one mole of a gas at normal temperature and pressure is _________ Litre.

  1. 11.2
  2. 22.4
  3. 33.3 
  4. 44.4

Answer (Detailed Solution Below)

Option 2 : 22.4

Mole Concept and Molecular Mass Question 8 Detailed Solution

Download Solution PDF

The correct answer is Option 2.

Key Points

  • One mole of an ideal gas occupies 22.4 liters at standard temperature and pressure (STP).
  • Standard temperature and pressure (STP) is defined as a temperature of 0°C (273.15 K) and a pressure of 1 atm (101.325 kPa).
  • This volume is known as the molar volume of a gas.
  • The concept is based on the Ideal Gas Law, which states that PV=nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is temperature.

Additional Information

  • Avogadro's Law: This law states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules.
  • Ideal Gas Law: The equation PV=nRT is used to describe the behavior of an ideal gas.
  • Gas Constant (R): The value of R in the Ideal Gas Law is 8.314 J/(mol·K) or 0.0821 L·atm/(mol·K).
  • Real Gases: Deviations from the Ideal Gas Law occur at high pressures and low temperatures where intermolecular forces become significant.
  • Molar Mass: The mass of one mole of a substance (element or compound) is expressed in grams per mole (g/mol).

In a compound having molecular formula XY, element 'X' belongs to the 3rd period and the 2nd group, whereas, element 'Y' belongs to the 2nd period and the 16th group. What is the relative molecular mass of the compound XY?

  1. 40u
  2. 35u
  3. 64u
  4. 50u

Answer (Detailed Solution Below)

Option 1 : 40u

Mole Concept and Molecular Mass Question 9 Detailed Solution

Download Solution PDF

The correct answer is 40u.

Key Points

  • Element 'X' belongs to the 3rd period and the 2nd group of the periodic table, which identifies it as Magnesium (Mg) with an atomic mass of 24u.
  • Element 'Y' belongs to the 2nd period and the 16th group of the periodic table, which identifies it as Oxygen (O) with an atomic mass of 16u.
  • The molecular formula XY indicates a 1:1 ratio of Magnesium to Oxygen in the compound.
  • The relative molecular mass is calculated as the sum of the atomic masses of X and Y: 24u (Mg) + 16u (O) = 40u.

Additional Information

  • Periodic Table:
    • The periodic table is a tabular arrangement of chemical elements, organized by their atomic number, electron configuration, and recurring chemical properties.
    • Elements are arranged in rows called periods and columns called groups.
  • Magnesium (Mg):
    • Magnesium is a chemical element with the symbol Mg and atomic number 12.
    • It is a shiny gray solid, often used in alloys and as a reducing agent in the production of metals.
  • Oxygen (O):
    • Oxygen is a chemical element with the symbol O and atomic number 8.
    • It is a highly reactive nonmetal and an oxidizing agent that readily forms oxides with most elements and compounds.
  • Relative Molecular Mass:
    • The relative molecular mass (molecular weight) of a molecule is the sum of the atomic masses of all the atoms in the molecule.
    • It is calculated using the atomic masses of the constituent elements as given in the periodic table.

Mole Concept and Molecular Mass Question 10:

How many moles of CO2 are present in a gas jar containing 1.506 × 1023 molecules of carbon dioxide? 

  1. 0.5
  2. 1
  3. 2
  4. 0.25

Answer (Detailed Solution Below)

Option 4 : 0.25

Mole Concept and Molecular Mass Question 10 Detailed Solution

The correct answer is 0.25

Concept:

Mole:

  • The mole is a unit of measurement for the amount of substance.
  • One mole of any substance contains exactly \(6.022 \times 10^{23}\) entities (this number is known as Avogadro's number \(N_A\).
  • Formula to calculate moles: \(n = \frac{N}{N_A}\)

Calculation:

Given,

Number of molecules of\( CO_2 = N = 1.506 \times 10^{23}\)

Avogadro's number, \(N_A = 6.022 \times 10^{23} \, \text{molecules/mol}\)

Number of moles of \(CO_2\),

\(n = \frac{N}{N_A}\)

\( n = \frac{1.506 \times 10^{23}}{6.022 \times 10^{23}}\)

⇒ \(n \approx 0.25 \ moles\)

∴ The number of moles of \( CO_2 \) present is 0.25.

Mole Concept and Molecular Mass Question 11:

The highest number of atoms is present in

  1. 0.40g Ca
  2. 12 g He
  3. 4 g He
  4. 46 g Na

Answer (Detailed Solution Below)

Option 2 : 12 g He

Mole Concept and Molecular Mass Question 11 Detailed Solution

CONCEPT:

Number of Atoms and Moles

  • The number of atoms in a given sample can be calculated using the concept of moles and Avogadro's number (6.022 × 1023 atoms per mole).
  • Moles of a substance can be calculated using the formula:

    Moles = Mass of the substance (in grams) / Molar mass (in g/mol)

  • The total number of atoms is then given by:

    Number of Atoms = Moles × Avogadro's number

EXPLANATION

1) 0.40 g Ca:

  • Molar mass of Ca = 40 g/mol
  • Moles of Ca = 0.40 g / 40 g/mol = 0.01 mol
  • Number of Atoms = 0.01 mol × 6.022 × 1023 = 6.022 × 1021

2) 12 g He:

  • Molar mass of He = 4 g/mol
  • Moles of He = 12 g / 4 g/mol = 3 mol
  • Number of Atoms = 3 mol × 6.022 × 1023 = 1.8066 × 1024

3) 4 g He:

  • Molar mass of He = 4 g/mol
  • Moles of He = 4 g / 4 g/mol = 1 mol
  • Number of Atoms = 1 mol × 6.022 × 1023 = 6.022 × 1023

4) 46 g Na:

  • Molar mass of Na = 23 g/mol
  • Moles of Na = 46 g / 23 g/mol = 2 mol
  • Number of Atoms = 2 mol × 6.022 × 1023 = 1.2044 × 1024

Comparing the number of atoms: The highest number of atoms is in 12 g He.

Therefore, the answer is 12 g He.

Mole Concept and Molecular Mass Question 12:

The mass of 0:5 mole of N2 gas is 

  1. 7 g
  2. 14 g
  3. 21 g
  4. 28 g

Answer (Detailed Solution Below)

Option 2 : 14 g

Mole Concept and Molecular Mass Question 12 Detailed Solution

CONCEPT:

Molar Mass and Mole Calculation

  • The molar mass of a substance is the mass of one mole of that substance, usually expressed in grams per mole (g/mol).
  • The molar mass of nitrogen gas (N2) can be calculated by adding the atomic masses of two nitrogen atoms.
  • The molar mass of a single nitrogen atom (N) is approximately 14 g/mol.

EXPLANATION:

  • For nitrogen gas (N2):
    • The molar mass of N2 = 14 g/mol (for one N atom) × 2 = 28 g/mol
  • To find the mass of 0.5 mole of N2 gas, we use the formula:
    • Mass = Number of moles × Molar mass
    • Mass = 0.5 moles × 28 g/mol
    • Mass = 14 grams

Therefore, the mass of 0.5 mole of N2 gas is 14 grams.

Mole Concept and Molecular Mass Question 13:

The volume of one mole of a gas at normal temperature and pressure is _________ Litre.

  1. 11.2
  2. 22.4
  3. 33.3 
  4. 44.4

Answer (Detailed Solution Below)

Option 2 : 22.4

Mole Concept and Molecular Mass Question 13 Detailed Solution

The correct answer is Option 2.

Key Points

  • One mole of an ideal gas occupies 22.4 liters at standard temperature and pressure (STP).
  • Standard temperature and pressure (STP) is defined as a temperature of 0°C (273.15 K) and a pressure of 1 atm (101.325 kPa).
  • This volume is known as the molar volume of a gas.
  • The concept is based on the Ideal Gas Law, which states that PV=nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is temperature.

Additional Information

  • Avogadro's Law: This law states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules.
  • Ideal Gas Law: The equation PV=nRT is used to describe the behavior of an ideal gas.
  • Gas Constant (R): The value of R in the Ideal Gas Law is 8.314 J/(mol·K) or 0.0821 L·atm/(mol·K).
  • Real Gases: Deviations from the Ideal Gas Law occur at high pressures and low temperatures where intermolecular forces become significant.
  • Molar Mass: The mass of one mole of a substance (element or compound) is expressed in grams per mole (g/mol).

Mole Concept and Molecular Mass Question 14:

In a compound having molecular formula XY, element 'X' belongs to the 3rd period and the 2nd group, whereas, element 'Y' belongs to the 2nd period and the 16th group. What is the relative molecular mass of the compound XY?

  1. 40u
  2. 35u
  3. 64u
  4. 50u

Answer (Detailed Solution Below)

Option 1 : 40u

Mole Concept and Molecular Mass Question 14 Detailed Solution

The correct answer is 40u.

Key Points

  • Element 'X' belongs to the 3rd period and the 2nd group of the periodic table, which identifies it as Magnesium (Mg) with an atomic mass of 24u.
  • Element 'Y' belongs to the 2nd period and the 16th group of the periodic table, which identifies it as Oxygen (O) with an atomic mass of 16u.
  • The molecular formula XY indicates a 1:1 ratio of Magnesium to Oxygen in the compound.
  • The relative molecular mass is calculated as the sum of the atomic masses of X and Y: 24u (Mg) + 16u (O) = 40u.

Additional Information

  • Periodic Table:
    • The periodic table is a tabular arrangement of chemical elements, organized by their atomic number, electron configuration, and recurring chemical properties.
    • Elements are arranged in rows called periods and columns called groups.
  • Magnesium (Mg):
    • Magnesium is a chemical element with the symbol Mg and atomic number 12.
    • It is a shiny gray solid, often used in alloys and as a reducing agent in the production of metals.
  • Oxygen (O):
    • Oxygen is a chemical element with the symbol O and atomic number 8.
    • It is a highly reactive nonmetal and an oxidizing agent that readily forms oxides with most elements and compounds.
  • Relative Molecular Mass:
    • The relative molecular mass (molecular weight) of a molecule is the sum of the atomic masses of all the atoms in the molecule.
    • It is calculated using the atomic masses of the constituent elements as given in the periodic table.
Get Free Access Now
Hot Links: teen patti master real cash teen patti list all teen patti teen patti master downloadable content teen patti boss