Heavy water contains 20% hydrogen by mass and 80% oxygen by mass.
Heavy water is water which contains the heavy isotope of hydrogen, Hydrogen-2 in its molecules.
The mass of heavy water is greater than that of water.
The molar mass of heavy water is 20.0 g
The percentage composition of the elements in heavy water are as follows:
Hydrogen = 2 × 2g/20 g ×100% = 20%
Oxygen = 16g/20g × 100% = 80%.
Therefore, Heavy water contains 20% hydrogen by mass and 80% oxygen by mass.
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