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"#
