Answer: 3.86x10^24 molecules
Explanation:
From Avogadro's hypothesis, we understood that 1mole of any substance contains 6.02x10^23 molecules.
This means that 1mole of H2O contains 6.02x10^23 molecules.
Therefore, 6.42 moles of H20 will contain = 6.42 x 6.02x10^23 = 3.86x10^24 molecules
