A chloride of silicon contains 79.1% by mass of Cl. What is the empirical formula of this silicon chloride?

• A. SiCl2
• B. SiCl3
• C. Si2Cl6
• D. SiCl4

Answer: (D)

Verified step by step guidance

1. Step 1: Assume a 100 g sample of the compound to simplify calculations. This means you have 79.1 g of Cl and the rest is Si, so 100 g - 79.1 g = 20.9 g of Si.
2. Step 2: Convert the masses of Si and Cl to moles by dividing by their respective atomic masses. Use the atomic mass of Si as approximately 28.09 g/mol and Cl as approximately 35.45 g/mol. Calculate moles of Si as \(\frac{20.9}{28.09}\) and moles of Cl as \(\frac{79.1}{35.45}\).
3. Step 3: Determine the mole ratio of Si to Cl by dividing both mole values by the smaller number of moles obtained in Step 2. This will give a ratio close to whole numbers.
4. Step 4: Use the mole ratio to write the empirical formula. The ratio of Si to Cl corresponds to the subscripts in the formula \(\mathrm{SiCl_x}\), where \(x\) is the mole ratio of Cl to Si.
5. Step 5: Compare the mole ratio to the given options and identify which empirical formula matches the ratio closest, confirming the correct formula is \(\mathrm{SiCl_4}\).