How many molecules are in a sample of water H2O that has a mass of 50.0g? Explain and show work.

To determine how many molecules are in a 50.0 g sample of water (H₂O), we need to follow a few steps:

1. Find the molar mass of water: The molar mass of water can be calculated using the atomic masses of its constituent elements. The atomic mass of hydrogen (H) is approximately 1.01 g/mol, and that of oxygen (O) is about 16.00 g/mol. Water has two hydrogen atoms and one oxygen atom, so the calculation is as follows:
   • 2 × 1.01 g/mol (for hydrogen) + 1 × 16.00 g/mol (for oxygen) = 2.02 g/mol + 16.00 g/mol = 18.02 g/mol.
2. Calculate the number of moles in 50.0 g of water: We can find the number of moles by dividing the mass of the sample by the molar mass:
   • Number of moles = mass / molar mass = 50.0 g / 18.02 g/mol ≈ 2.77 moles.
3. Convert moles to molecules: Using Avogadro’s number (approximately 6.022 × 10²³ molecules/mol), we can determine how many molecules are in 2.77 moles:
   • Number of molecules = moles × Avogadro’s number = 2.77 moles × 6.022 × 10²³ molecules/mol ≈ 1.67 × 10²⁴ molecules.

In conclusion, a 50.0 g sample of water contains approximately 1.67 × 10²⁴ molecules.