How many atoms are there in 9 grams of water?

First, we determine the number of moles of the substance, for which the total mass must be divided by molar:
9/18 = 0.5 moles
To determine the number of molecules, it is enough to multiply the number of moles by Avogadro’s number (Na = 6.022 * 10 ^ 23), in this case we get:
0.5 * 6.022 * 10 ^ 23 = 3.011 * 10 ^ 23

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