Final answer:
The percentage of nitrogen in the coal sample is calculated by determining the mass of nitrogen in the produced ammonia and dividing by the mass of the coal sample, then multiplying by 100. Correct answer is not mentioned in option.
Step-by-step explanation:
The student asked about the percentage of nitrogen in a coal sample after an experiment where 17 mg of ammonia gas was produced from a 2-gram coal sample. To determine the percentage of nitrogen, we first need to understand that ammonia (NH₃) consists of one atom of nitrogen and three atoms of hydrogen. The molar mass of ammonia is 17 g/mol (14 g/mol for nitrogen and 1 g/mol for each hydrogen), meaning each mole of ammonia contains 14 g of nitrogen.
Since the experiment produced 17 mg of ammonia, this is equivalent to 0.017 g. Using the molar mass of ammonia, we can find out how much nitrogen was in the 0.017 g of ammonia by setting up a proportion based on the molar mass:
14 g N in 17 g NH₃
x g N in 0.017 g NH₃
Solving for x gives us the mass of nitrogen, which we then divide by the total mass of the coal sample (2 g) and multiply by 100 to get the percentage of nitrogen in the coal:
x = (14 g N / 17 g NH₃) × 0.017 g NH₃
x = 0.014 g N
Percentage of nitrogen = (0.014 g N / 2 g coal) × 100%
This calculation yields a value of 0.7%, which is not an option provided in the question, indicating a possible error in the available choices or question details. However, based on the closest available option, one might select 0.85%, which is the most similar to the calculated percentage but is not strictly accurate.