Question

Pure water is a compound. It contains 11.19% by mass of hydrogen and oxygen by mass of ________. (88.81% , 31.81%)
Choose the correct answer

Answer 1

31.81 % would be the mass of Oxygen

Answer 2

Answer: The oxygen by mass in water is 88.81 %.

Explanation:

Pure water has a chemical formula of $H_2O$. It is made up from hydrogen and oxygen atoms.

We are given:

11.19 % by mass of hydrogen is present in pure water.

This means that 11.91 grams of hydrogen is present in 100 grams of pure water.

So, amount of oxygen present in pure water = (100 - 11.19) = 88.81 g

Calculating the mass percent of oxygen in pure water:

$\text{Mass percent of oxygen}=\frac{\text{Mass of oxygen}}{\text{Mass of pure water}}\times 100$

Mass of pure water = 100 g

Mass of oxygen = 88.81 g

Putting values in above equation, we get:

$\text{Mass percent of oxygen}=\frac{88.81g}{100g}\times 100=88.81\%$

Hence, the oxygen by mass in water is 88.81 %.