In 10 minutes. boiling evaporated 120 g of water. How many water molecules went from

In 10 minutes. boiling evaporated 120 g of water. How many water molecules went from a liquid to a vapor state every second?

1) Find how many grams of water evaporated every second
120 [gr] / 600 [sec] = 0.2 [gr / sec]

2) Find the mass of one water molecule.
– A water molecule contains 1 oxygen atom and 2 hydrogen atoms. According to the periodic table, we find that the relative atomic mass of oxygen is 16, and that of hydrogen is 1.
– So the molar mass is 2 * 1 + 16 = 18 g / mol.
– Then the mass of one water molecule is 18 / (6 * 10 ^ 23) ~ = 3 * 10 ^ (- 23) gr. (where 6 * 10 ^ 23 is Avogadro’s number)

3) Let’s calculate how many water molecules have evaporated every second.
0.2 [gr / sec] / 3 * 10 ^ (- 23) [gr] ~ = 6.67 * 10 ^ 21 [pcs / sec]

Answer: 6.67 * 10 ^ 21 molecules evaporated every second.