A compound is found to contain 53.5% carbon, 15.5% hydrogen, and 31.0% nitrogen by mass. What is the empirical formula of this substance?

• A. C3H9N2
• B. C2H7N
• C. CH5N
• D. C4H10N

Answer: (B)

Verified step by step guidance

1. Convert the given mass percentages of each element into moles by assuming a 100 g sample. This means the mass of each element in grams is equal to its percentage: 53.5 g C, 15.5 g H, and 31.0 g N.
2. Calculate the number of moles of each element using their atomic masses: Carbon (C) = 12.01 g/mol, Hydrogen (H) = 1.008 g/mol, and Nitrogen (N) = 14.01 g/mol. Use the formula \(\text{moles} = \frac{\text{mass}}{\text{atomic mass}}\) for each element.
3. Determine the simplest whole number mole ratio by dividing the moles of each element by the smallest number of moles calculated among the three elements.
4. If any of the ratios are not whole numbers, multiply all ratios by the smallest factor that converts them into whole numbers (e.g., 2, 3, 4, etc.).
5. Write the empirical formula by using the whole number mole ratios as subscripts for each element in the order C, H, and N.