Step 1. Calculate the mass of the water
"Mass" = 1000 color(red)(cancel(color(black)("mL water"))) × "1 g water"/(1 color(red)(cancel(color(black)("mL water")))) = "1000 g water"
Step 2. Calculate the moles of water
"Moles of water" = 1000 color(red)(cancel(color(black)("g water"))) × "1 mol water"/(18.02 color(red)(cancel(color(black)("g water")))) = "55.49 mol water"
Step 3. Calculate the molecules of water
"Molecules of H"_2"O" = 55.49 color(red)(cancel(color(black)("mol H"_2"O"))) × (6.022 × 10^23 color(white)(l)"molecules H"_2"O")/(1 color(red)(cancel(color(black)("mol H"_2"O"))))
= 3.342 × 10^25 color(white)(l)"molecules H"_2"O"
Step 4. Calculate the number of atoms
Each molecule of "H"_2"O" contains three atoms.
∴ "No. of atoms" = 3.342 × 10^25 color(red)(cancel(color(black)("molecules H"_2"O"))) × "3 atoms"/(1 color(red)(cancel(color(black)("molecule H"_2"O"))))
= 1.00 × 10^26 color(white)(l)"atoms"
