We can find the number of moles of water at STP conditions using the ideal gas law equation PV = nRT Where P - standard pressure - 1 atm V - 22.4 L n - number of moles R - universal gas constant - 0.0821 L.atm/mol.K T - standard temperature- 273 K Substituting the values in the equation 1 atm x 22.4 L = n x 0.082057 L.atm/mol.K x 273 K n = 1.00 mol Therefore number of water moles are 1.00 in 22.4 L This is called the molar volume, 1 mol of any gas occupies a volume of 22.4 L at STP Molar mass of H2O is 18.02 g/mol Mass of water is 18.02 g/mol Answer is A. 18.02 g/mol
