1. Atomic mass of Na = 23u (Given) Then, gram atomic mass of Na = 23g Now, 23g of Na contains = 6.022×10²³ number of atoms Thus, 100g of Na contains = 6.022×10²³ ×100/23 number of atoms = 2.6182 × 10²⁴ number of atoms Again, atomic mass of Fe = 56u (Given) Then, gram atomic mass of Fe = 56g Now, 56 g oRead more

    Atomic mass of Na = 23u (Given)
    Then, gram atomic mass of Na = 23g
    Now, 23g of Na contains = 6.022×10²³ number of atoms
    Thus, 100g of Na contains = 6.022×10²³ ×100/23 number of atoms
    = 2.6182 × 10²⁴ number of atoms
    Again, atomic mass of Fe = 56u (Given)
    Then, gram atomic mass of Fe = 56g
    Now, 56 g of Fe contains = 6.022×10²³ number of atoms
    Thus, 100 g of Fe
    6.022×10²³ ×100/56 number of atoms
    = 1.0753 × 10²⁴number of atoms
    Therefore, 100 grams of sodium contain more number of atoms than 100 grams of iron.

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  2. One mole of carbon atoms weighs 12g (Given) i.e., mass of 1 mole of carbon atoms = 12g Then, mass of 6.022× 10²³ number of carbon atoms = 12g Therefore, mass of 1 atom of carbon = 12/6.022×10²³ g = 1.9926 × 10⁻²³ g For more answers visit to website: https://www.tiwariacademy.com/ncert-solutions/clasRead more

    One mole of carbon atoms weighs 12g (Given)
    i.e., mass of 1 mole of carbon atoms = 12g
    Then, mass of 6.022× 10²³ number of carbon atoms = 12g
    Therefore, mass of 1 atom of carbon = 12/6.022×10²³ g
    = 1.9926 × 10⁻²³ g

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  3. Formula unit mass of ZnO = Atomic mass of Zn + Atomic mass of O = 65 + 16 = 81u Formula unit mass of Na₂O = 2 × Atomic mass of Na + Atomic mass of O = 2 × 23 + 16 = 62u Formula unit mass of K₂CO₃ = 2 × Atomic mass of K + Atomic mass of C + 3 × Atomic mass of O = 2 × 39 + 12 + 3 × 16 = 138u For moreRead more

    Formula unit mass of ZnO = Atomic mass of Zn + Atomic mass of O
    = 65 + 16 = 81u
    Formula unit mass of Na₂O = 2 × Atomic mass of Na + Atomic mass of O
    = 2 × 23 + 16 = 62u
    Formula unit mass of K₂CO₃
    = 2 × Atomic mass of K + Atomic mass of C + 3 × Atomic mass of O
    = 2 × 39 + 12 + 3 × 16 = 138u

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  4. Molecular mass of H₂ = 2 × Atomic mass of H = 2 × 1 = 2u Molecular mass of O₂ = 2 × Atomic mass of O = 2 × 16 = 32u Molecular mass of Cl₂ = 2 × Atomic mass of Cl = 2 × 35.5 = 71u Molecular mass of CO₂ = Atomic mass of C + 2 × Atomic mass of O = 12 + 2 × 16 = 44u Molecular mass of CH₄ = Atomic mass oRead more

    Molecular mass of H₂ = 2 × Atomic mass of H
    = 2 × 1 = 2u
    Molecular mass of O₂ = 2 × Atomic mass of O
    = 2 × 16 = 32u
    Molecular mass of Cl₂ = 2 × Atomic mass of Cl
    = 2 × 35.5 = 71u
    Molecular mass of CO₂ = Atomic mass of C + 2 × Atomic mass of O
    = 12 + 2 × 16 = 44u
    Molecular mass of CH₄ = Atomic mass of C + 4 × Atomic mass of H
    = 12 + 4 × 1 = 16u
    Molecular mass of C₂H₆ = 2 × Atomic mass of C + 6 × Atomic mass of H
    = 2 × 12 + 6 × 1 = 30u
    Molecular mass of C₂H₄ = 2 × Atomic mass of C + 4 × Atomic mass of H
    = 2 × 12 + 4 × 1 = 28u
    Molecular mass of NH₃ = Atomic mass of N + 3 × Atomic mass of H
    = 14 + 3 × 1 =17u
    Molecular mass of CH₃OH Atomic mass of C+4 ×Atomic mass of H+Atomic mass of O
    = 12 + 4 × 1 + 16 = 32u

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  5. (i) In an H₂S molecule, three atoms are present; two of hydrogen and one of sulphur. (ii) In a PO₄₃- ion, five atoms are present; one of phosphorus and four of oxygen. For more answers visit to website: https://www.tiwariacademy.com/ncert-solutions/class-9/science/chapter-3/

    (i) In an H₂S molecule, three atoms are present; two of hydrogen and one of sulphur.
    (ii) In a PO₄₃- ion, five atoms are present; one of phosphorus and four of oxygen.

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