Answer:
Step-by-step explanation:
Given 7 moles H₂O
By definition, the 'mole', in chemical process, is the mass of substance (usually in grams and includes elements or molecules) that contain 6.023 x 10²³ particles (Avogadro's Number) of the given substance. The mole is also related (or, equal) to the following:
1 mole = 1 Avogadro's number of particles = 6.023 x 10²³ particles = 1 formula wt. = 1 molecular wt. = 1 gram formula weight
So, if given 7 moles of water (H₂O) => ? molecules of water (H₂O)
By the Avogadro relationship => 1 mole H₂O = 6.023 x 10²³ molecules of H₂O
Then 7 moles H₂O => 7 moles x 6.023 x 10²³ molecules H₂O/mole H₂O
= 4.216 x 10²⁴ water molecules.
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General FYI note ... if needed ...
The subscripts identify number of moles of element in one mole of formula weight. That is while 1 mole H₂O contains 6.023 x 10²³ molecules of water it also contains 2 moles of hydrogen or, 2 x 6.02 x 10²³ atoms of hydrogen and moles of oxygen 1 x 6.023 x 10²³ atoms of oxygen.