Mole Concept (Class 11 Chemistry)

Master the mole as the central concept connecting atomic mass, molecular mass, and stoichiometry in chemistry.

Mole Concept (Class 11 Chemistry)

Master the mole as the central concept connecting atomic mass, molecular mass, and stoichiometry in chemistry.

✓ 100% Free ✓ No Login Needed ✓ NCERT / CBSE Aligned ✓ Download as PDF

TL;DR: Master the mole as the central concept connecting atomic mass, molecular mass, and stoichiometry in chemistry.

Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated

🤖 Stuck on any question? Ask Syllab's free AI Tutor for a step-by-step explanation — instant, unlimited, no login.

Master the mole as the central concept connecting atomic mass, molecular mass, and stoichiometry in chemistry.

Mole Concept MCQs with Answers & Explanations

Q1. What is a mole?

  1. Unit of mass
  2. One gram of substance
  3. A small amount
  4. Avogadro number of particles ✓ (correct)

Explanation: A mole is the SI unit of amount of substance. One mole contains Avogadro's number (6.02 × 10²³) of particles (atoms, molecules, or ions).

Q2. What is Avogadro's number?

  1. 6.02 × 10²³ ✓ (correct)
  2. 9.81
  3. 3.14
  4. 1.67 × 10⁻²⁷

Explanation: Avogadro's number is 6.02 × 10²³. It is the number of particles in one mole of any substance.

Q3. What is molar mass?

  1. Half of atomic mass
  2. Mass of one mole of substance ✓ (correct)
  3. Number of particles
  4. Density of substance

Explanation: Molar mass is the mass of one mole of a substance in grams per mole (g/mol). It numerically equals the relative molecular mass.

Q4. How many moles are in 32 g of oxygen gas (O₂)? (Atomic mass of O = 16)

  1. 2 moles
  2. 32 moles
  3. 1 mole ✓ (correct)
  4. 0.5 moles

Explanation: Molar mass of O₂ = 2 × 16 = 32 g/mol. Moles = mass / molar mass = 32 / 32 = 1 mole.

Q5. What is the relationship between moles, mass, and molar mass?

  1. Moles = molar mass - mass
  2. Moles = mass + molar mass
  3. Moles = mass × molar mass
  4. Moles = mass / molar mass ✓ (correct)

Explanation: The relationship is: number of moles = mass (g) / molar mass (g/mol). This is a fundamental equation in chemistry.

Q6. How many atoms are in 2 moles of carbon?

  1. 2 × 6.02 × 10²³ ✓ (correct)
  2. 6.02 × 10²³
  3. 0.5 × 6.02 × 10²³
  4. 3 × 6.02 × 10²³

Explanation: Each mole contains 6.02 × 10²³ atoms. Therefore, 2 moles contain 2 × 6.02 × 10²³ = 1.204 × 10²⁴ atoms.

Q7. What is the molar volume of a gas at STP?

  1. 11.2 L/mol
  2. 22.4 L/mol ✓ (correct)
  3. 5.6 L/mol
  4. 44.8 L/mol

Explanation: At STP (Standard Temperature and Pressure: 0°C and 1 atm), one mole of any ideal gas occupies 22.4 liters.

Q8. What is molecular mass?

  1. Mass of one mole
  2. Density of molecule
  3. Sum of atomic masses in a molecule ✓ (correct)
  4. Mass of one atom

Explanation: Molecular mass is the sum of atomic masses of all atoms in a molecule. It is expressed in atomic mass units (u).

Q9. Calculate the number of molecules in 4.4 g of CO₂. (C = 12, O = 16)

  1. 2 × 6.02 × 10²³
  2. 0.5 × 6.02 × 10²³
  3. 6.02 × 10²³
  4. 0.1 × 6.02 × 10²³ ✓ (correct)

Explanation: Molar mass of CO₂ = 12 + 32 = 44 g/mol. Moles = 4.4/44 = 0.1, so molecules = 0.1 x 6.02 x 10²³.

Q10. What is empirical formula?

  1. Simplest whole number ratio of atoms ✓ (correct)
  2. Number of atoms in molecule
  3. Actual formula of compound
  4. Molecular structure

Explanation: Empirical formula shows the simplest whole number ratio of atoms in a compound. Molecular formula shows the actual number of atoms.

Frequently Asked Questions

What is the difference between atomic mass unit and molar mass?

Atomic mass unit (u) is for individual atoms. Molar mass (g/mol) is for one mole of particles. Numerically they are equal but units differ.

How is the mole concept used in stoichiometry?

Stoichiometry uses mole ratios from balanced equations to calculate reactants needed and products formed in chemical reactions.

🤖 Stuck on any of these? Ask Syllab's free AI Tutor to explain step by step →