An atom is an extremely small particle and no device is capable of isolating an atom from sample or counting the number of atoms in the sample. The only way to identify the amount of atoms present in a sample is by using the following equation Moles of a substance = (grams of the substance)/(MW of that substance) It is easy to calculate the MW of a substance with the help of a periodic table If you know the mass of substance, simply divide the mass by the MW of that substance to find the amount of moles present. A mole of substance contains 6.022 X 1023 molecules (if weighing a compound, like H20. glucose etc) or 6.022 X 102 atoms (if weighing a pure element like gold, Cu, silver etc) Question: Calculate the moles of water present in a 500.0 ml drinking water bottle. The density of water = 1.08/1.0 mL. TH. 5016 Hint: use unit conversion to find the mass of 500 mL of water 27.7777 moles of water B 0,02777 moles of water 2.7777 moles of water D 1.0 mole of water