Before we find the number of moles of H₂O that we have in the 97.3 g sample of it, we have to find the molar mass of H₂O. We are given the molar mass of H and O.
H = 1.008 g/mol O = 16.00 g/mol
One molecule of H₂O has 2 atoms of H and 1 atom of O. We can calculate its molar mass like this:
molar mass of H₂O = 2 * molar mass of H + 1 * molar mass of O
molar mass of H₂O = 2 * 1.008 g/mol + 1 * 16.00 g/mol
molar mass of H₂O = 18.016 g/mol
Now that we know that 1 mol of H₂O has a mass of 18.016 g, we can find the number of moles of H₂O that there are in 97.3 g of it.
number of moles of H₂O = mass of H₂O/molar mass of H₂O
number of moles of H₂O = 97.3 g/(18.016 g/mol)
number of moles of H₂O = 5.40 moles
Answer: there are 5.40 moles of water in 97.3 g of it.