Chemistry Class 11: Mole Concept
Introduction
- Overview of the mole concept.
- Importance for board and competitive exams.
Key Formulas
- Number of Moles (Molecules)
- Formula: Mass given / Gram Molecular Mass
- Number of Moles (Atoms)
- Formula: Mass given / Gram Atomic Mass
- Number of Moles (Volume)
- Formula: Volume given / Molar Volume
- Number of Molecules/Atoms
- When moles or mass is given, use appropriate formulas to calculate.
Practice Problems
Question 1: Moles in Water
- Problem: How many moles are present in 180 grams of water?
- Solution:
- Water molecule: H₂O
- Molecular mass of water: 18 grams (2xH + O = 2x1 + 16)
- Calculation: 180 / 18 = 10 moles
Question 2: Moles in Carbon Dioxide
- Problem: Moles present in 44.8 liters of CO₂ at STP.
- Solution:
- Volume given: 44.8 liters
- Molar Volume: 22.4 liters
- Calculation: 44.8 / 22.4 = 2 moles
Question 3: Atoms in Ammonia
- Problem: Total number of atoms in 34 grams of NH₃.
- Solution:
- Atomicity of NH₃: 4 (1 Nitrogen + 3 Hydrogen)
- Moles: 34 / 17 = 2 moles (Molecular mass of NH₃: 14 + 3)
- Number of Atoms: 2 moles x 6.022 x 10²³ x 4 = Result
Question 4: Oxygen Atoms in Carbon Dioxide
- Problem: Oxygen atoms in 88 grams of CO₂.
- Solution:
- Atomicity: 2 oxygen atoms
- Moles: 88 / 44 = 2 moles (Molecular mass of CO₂: 12 + 32)
- Number of Oxygen Atoms: 2 x 6.022 x 10²³ x 2 = Result
Question 5: Electrons in Methane
- Problem: Electrons in 1.6 grams of CH₄.
- Solution:
- Atomic number: Carbon = 6, Hydrogen = 1
- Electrons in CH₄: 10 (6 from Carbon, 4 from Hydrogen)
- Moles: 1.6 / 16
- Number of Electrons: Moles x 6.022 x 10²³ x 10 = Result
Additional Questions
- Calculate the number of atoms in 52 moles of Argon:
- Calculate the number of atoms in 52U of Helium:
- Calculate the number of atoms in 52 grams of Helium:
- Moles: 52 / 4
- Number of Atoms: Moles x 6.022 x 10²³
Conclusion
- Practice is key to mastering the mole concept.
- Upcoming topic: Stoichiometry.
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