Question

1. calculate the mass percent of each element in water.

Explanation:

Step1: Determine molar - mass of water

The chemical formula of water is $H_2O$. The molar mass of hydrogen ($H$) is approximately $1\ g/mol$, and the molar mass of oxygen ($O$) is approximately $16\ g/mol$. The molar mass of $H_2O$ is $2\times1 + 16=18\ g/mol$.

Step2: Calculate mass - percent of hydrogen

The mass of hydrogen in one mole of water is $2\times1 = 2\ g$. The mass - percent of hydrogen, $w_H=\frac{2}{18}\times100\%\approx11.1\%$.

Step3: Calculate mass - percent of oxygen

The mass of oxygen in one mole of water is $16\ g$. The mass - percent of oxygen, $w_O=\frac{16}{18}\times100\%\approx88.9\%$.

Answer:

The mass percent of hydrogen in water is approximately $11.1\%$ and the mass percent of oxygen in water is approximately $88.9\%$.