Final answer:
The percent by mass of hydrogen in NH₃ is found by dividing the total mass of hydrogen by the molecular mass of ammonia and multiplying by 100%. The closest given option to this value is A. 17.6%.
Step-by-step explanation:
To calculate the percent by mass of hydrogen in NH₃, we need to consider the molecular mass of NH₃, which is 17.0 grams/mol, as given. Ammonia (NH₃) consists of one nitrogen atom and three hydrogen atoms. The relative atomic mass of nitrogen (N) is approximately 14.0, and the relative atomic mass of hydrogen (H) is approximately 1.01 for each atom.
Firstly, we calculate the total mass of the hydrogen atoms in one mole of NH₃: Mass of hydrogen in NH₃ = 3 × 1.01 g/mol = 3.03 g/mol Then, we calculate the percent by mass of hydrogen: Percent by mass of H = (Mass of hydrogen / Molecular mass of NH₃) × 100%.
Plugging in the values, we get: Percent by mass of H = (3.03 g/mol / 17.0 g/mol) × 100% ≈ 17.8%. The percent by mass of hydrogen in NH₃ is approximately 17.8%. Thus, the correct answer is A. 17.6%, as it is the closest option given.