Question

Water is always made up of _____ part hydrogen to ______parts oxygen by mass.

Answer 1

I believe it's two part hydrogen and one part oxygen (H20)

Answer 2

The formula of water is $H_{2}O$. Thus, molar ratio is 2:1.

Thus,

$n_{H}:n_{O}=2:1$

Number of moles are related to mass and molar mass as follows:

$n=\frac{m}{M}$

Here, m is mass and M is molar mass

Molar mass of hydrogen is 1 g/mol and that of oxygen is 16 g/mol

$\frac{n_{H}}{n_{O}}=\frac{2}{1}$

Converting molar ratio into mass ratio as follows:

$\frac{\frac{m_{H}}{M_{H}}}{\frac{m_{O}}{M_{O}}}=\frac{2}{1}$

Also,$\frac{m_{H\times M_{H}}}{m_{O}\times M_{O}}=\frac{2}{1}$

Putting the values of molar mass,

$\frac{m_{H\times 1 }}{m_{O}\times 16}=\frac{2}{1}$

Thus,

$\frac{m_{H}}{m_{O}}=\frac{16\times 2}{1}=\frac{32}{1}$

Thus, water is always made up of 32 part hydrogen to 1 part oxygen by mass.