Sam asked in Science & MathematicsChemistry · 7 years ago

Calculate the number of H2O molecules in a human body of mass 56.9 kg.?

Calculate the number of H2O molecules in a human body of mass 56.9 kg. Assume that, on average, water makes up 62% of the mass of a human body. (Use 1.0 u for the atomic mass of hydrogen, and 16.0 u for the atomic mass of oxygen

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  • 7 years ago
    Best Answer

    56.9 * 0.62 = 35.278 kg of water in the body

    35.278 kg of H20 = x moles

    x = 35278/ Mr of water(18g) = 1959.889 moles of water

    1 mole of water = Agravados constant of molecules per mole = 6.022 * 10^23 * mol^-1

    Therefore 1959.889 moles of water = (1959.889 * 6.022 * 10^23) molecules in a human body of 56.9kg

    Answer: approximately 1.180 * 10^27 molecules.

    Hope it's right! :)

    Source(s): I have some knowledge of chemistry.
  • 4 years ago

    calculate number h2o molecules human body mass 785 kg assume average water

  • 7 years ago

    62% of 56.9 kg = 35.3 kg = 35 300 g

    find the number of mol:

    18.0 g = 1 mol of H2O

    35 300 g = 1960 mol of H2O

    find the number of molecules:

    1 mol = 6,022 * 10^23 molecules (Avogadro's number)

    1960 mol = 1.18 * 10^27 molecules

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