Question

Calculate the mass of hydrogen in 50ml of water.The water has 11 percent hydrogen and 89 percent oxygen.

Answer 1

The mass of hydrogen is 5.5g.

1st) We are going to assume that the density of water is 1g/ml, so using the density formula and replacing the volume on it, we can calculate the mass of water:

$\begin{gathered} \text{density}=\frac{mass}{volume} \\ 1g\mathrm{}ml^{-1}=\frac{mass}{50ml} \\ \text{mass}=1gml^{-1}\text{.}50ml \\ \text{mass}=50g \end{gathered}$

Now we know that the mass of water is 50g.

2nd) The mass of water calculated (50g) represents the 100% of the mass.

With the percent of hydrogen, we can calculate the mass of hydrogen:

$\begin{gathered} 100\%-50g \\ 11\%-x=\frac{11\%\cdot50g}{100\%} \\ x=5.5g \end{gathered}$

If 100% represents 50g of water, then the 11% of hydrogen in the water represents 5.5g.

So, the mass of hydrogen in 50ml of water is 5.5g.