A compound is found to be 83.7% carbon and 16.3% hydrogen by mass. What is the empirical formula of this compound?

• A. C3H8
• B. CH2
• C. CH4
• D. C2H5

Answer: (D)

Verified step by step guidance

1. Step 1: Assume you have 100 grams of the compound. This means you have 83.7 grams of carbon (C) and 16.3 grams of hydrogen (H).
2. Step 2: Convert the masses of each element to moles by dividing by their atomic masses: use 12.01 g/mol for carbon and 1.008 g/mol for hydrogen. Calculate moles of C as \(\frac{83.7}{12.01}\) and moles of H as \(\frac{16.3}{1.008}\).
3. Step 3: Determine the simplest mole ratio by dividing both mole values by the smaller number of moles obtained in Step 2. This will give you the relative number of atoms of each element in the empirical formula.
4. Step 4: If the mole ratios are not whole numbers, multiply both ratios by the smallest factor that converts them into whole numbers (e.g., 2, 3, 4, etc.).
5. Step 5: Write the empirical formula using the whole number mole ratios as subscripts for each element. For example, if the ratio is approximately 2 moles of C to 5 moles of H, the empirical formula is \(\mathrm{C_2H_5}\).