Estimate the number of h20 molecules in a human body of mass 80.2 kg. Assume that, on average, water makes up about 62 % of the mass of a human body.

To estimate the number of H2O molecules in a human body of mass 80.2 kg, we need to follow these steps:

1. Calculate the mass of water in the human body:
Given that water makes up about 62% of the mass, we can calculate it as follows:
Mass of water = 0.62 * 80.2 kg

2. Calculate the number of moles of water:
Since the molar mass of water (H2O) is approximately 18 g/mol, we need to convert the mass of water to moles:
Mass of water (in grams) = Mass of water (in kg) * 1000
Number of moles of water = Mass of water (in grams) / Molar mass of water

3. Calculate the number of molecules:
One mole of any substance contains Avogadro's number of particles, which is 6.022 × 10^23. Therefore, we can calculate the number of molecules:
Number of molecules = Number of moles of water * Avogadro's number

Let's calculate it step by step:

1. Mass of water = 0.62 * 80.2 kg = 49.724 kg

2. Mass of water (in grams) = 49.724 kg * 1000 = 49,724 grams
Number of moles of water = 49,724 grams / 18 g/mol ≈ 2,762.44 moles

3. Number of molecules = 2,762.44 moles * 6.022 × 10^23 molecules/mole
≈ 1.663 × 10^27 molecules

Therefore, there are approximately 1.663 × 10^27 H2O molecules in a human body of mass 80.2 kg.