The mass of hydrogen to the mass of oxygen in water is always _____ in ratio.

The chemical formula of water= H₂O

Mass of 1 hydrogen atom= 1 u

Mass of 2 hydrogen atoms= $2\times 1 u= 2 u$

Mass of 1 oxgen atom= 16 u

The mass ratio of hydrogen to oxygen in water is = $\frac{2 u}{16 u}=\frac{1}{8}$

Hence, whatever the source of water, the mass of hydrogen to the mass of oxygen in a compound such as water is always 1:8. As a result, decomposing 9 g of water yields 1 g of hydrogen and 8 g of oxygen every time.