11.19%. To replicate this result, follow these simple steps:
Determine the molecular weight of water as the sum of the atomic mass of all atoms in one molecule. 2 × 1.008 + 15.999 = 18.015 amu.
Obtain the molar mass of water as the numerical equivalent of its molecular weight, when expressed in g/mol. Molar mass of water = 18.015 g/mol.
Compute the mass of hydrogen in one mole of water as the numerical equivalent of the atomic mass of hydrogen atoms in one water molecule, when expressed in g/mol. Mass of hydrogen in 1 mol water = 2 × 1.008 = 2.016 g/mol.
Calculate the mass percent composition of hydrogen in water as (mass of hydrogen in 1 mol water/molar mass of water) × 100 = (2.016/18.015) × 100 = 11.19%.
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