A chloride of rhenium contains 63.6% rhenium by mass. What is the empirical formula of this compound?

• A. ReCl4
• B. ReCl3
• C. Re2Cl7
• D. ReCl2

Answer: (B)

Verified step by step guidance

1. Step 1: Assume you have 100 grams of the compound. This means you have 63.6 grams of rhenium (Re) and the remaining 36.4 grams is chlorine (Cl).
2. Step 2: Convert the masses of each element to moles by dividing by their atomic masses. Use the atomic mass of rhenium (Re) as approximately 186.21 g/mol and chlorine (Cl) as approximately 35.45 g/mol. Calculate moles of Re as \(\frac{63.6}{186.21}\) and moles of Cl as \(\frac{36.4}{35.45}\).
3. Step 3: Determine the simplest whole number mole ratio by dividing both mole values by the smaller of the two mole amounts obtained in Step 2.
4. Step 4: If the mole ratio is not a whole number, multiply both ratios by the smallest number that converts them into whole numbers (e.g., 2, 3, or 4).
5. Step 5: Write the empirical formula using the whole number mole ratios as subscripts for Re and Cl, respectively.