Calculate (to 1 d.p.) the percentage mass in water, [tex]H_2O[/tex], of Oxygen
Answer (2)
The percentage mass of oxygen in water (H₂O) is approximately 88.9%. This is calculated using the atomic masses of hydrogen and oxygen and the molecular mass of water. The final result is rounded to one decimal place for clarity.
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Determine the relative atomic masses of Hydrogen (1) and Oxygen (16).
Calculate the relative molecular mass of water ( H 2 O ): 2 × 1 + 16 = 18 .
Calculate the percentage mass of oxygen in water: 18 16 × 100 = 88.888... .
Round the result to 1 decimal place: 88.9 % .
Explanation
Problem Analysis We want to calculate the percentage mass of oxygen in water ( H 2 O ), rounded to 1 decimal place. To do this, we need to know the relative atomic masses of hydrogen (H) and oxygen (O).
Atomic Masses The relative atomic mass of hydrogen (H) is approximately 1, and the relative atomic mass of oxygen (O) is approximately 16.
Molecular Mass of Water Next, we calculate the relative molecular mass of water ( H 2 O ). Water has 2 hydrogen atoms and 1 oxygen atom, so the molecular mass is: 2 × atomic mass of H + atomic mass of O = 2 × 1 + 16 = 2 + 16 = 18
Mass of Oxygen The mass of oxygen in one molecule of water is simply the atomic mass of oxygen, which is 16.
Percentage Mass Calculation Now we calculate the percentage mass of oxygen in water using the formula: molecular mass of water mass of oxygen × 100 = 18 16 × 100
Rounding to 1 Decimal Place 18 16 × 100 = 0.8888... × 100 = 88.888... Rounding this to 1 decimal place, we get 88.9%.
Final Answer Therefore, the percentage mass of oxygen in water ( H 2 O ) is approximately 88.9%.
Examples
Understanding the percentage composition of elements in compounds is crucial in various fields. For example, in environmental science, knowing the percentage of oxygen in water helps assess water quality and its ability to support aquatic life. In chemistry, this calculation is fundamental for stoichiometry and understanding chemical reactions. In everyday life, it helps understand the basic composition of substances we use daily.
