Calculate the number of H2O molecules in a human body of mass 66.5 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.)
1
mass body = 66.5 kg = 66,500 g.
mass H2O = 66,500 x 0.62 = ?
mols H2O = ?g/18 = ?
Then remember 1 mol contains 6.02E23 molecules.
42molécules
To calculate the number of H2O molecules in a human body, we first need to determine the mass of water in the body.
We are given that water makes up 62% of the mass of a human body. Therefore, we can calculate the mass of water using the following equation:
Mass of water = (62/100) * Mass of human body
Substituting the given values:
Mass of water = (62/100) * 66.5 kg
Mass of water = 41.23 kg
Next, we need to calculate the number of moles of water. We can use the molar mass of water, which is the sum of the atomic masses of hydrogen (H) and oxygen (O).
Molar mass of H2O = (2 * atomic mass of H) + atomic mass of O
Molar mass of H2O = (2 * 1.0 u) + 16.0 u
Molar mass of H2O = 18.0 u
Now we determine the number of moles of water:
Number of moles of water = Mass of water / Molar mass of H2O
Number of moles of water = 41.23 kg / 18.0 g/mol
Number of moles of water ≈ 2.29 mol
Finally, we can calculate the number of molecules of water by multiplying the number of moles by Avogadro's number, which is approximately 6.022 x 10^23 molecules/mol.
Number of molecules of water = Number of moles of water * Avogadro's number
Number of molecules of water = 2.29 mol * 6.022 x 10^23 molecules/mol
Number of molecules of water ≈ 1.38 x 10^24 molecules
Therefore, there are approximately 1.38 x 10^24 H2O molecules in a human body with a mass of 66.5 kg.