Multiple Choice
Which of the following represents the empirical formula for the compound with the molecular formula x_4y_8?
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3. Chemical Reactions
Empirical Formula
Multiple Choice
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
Verified step by step guidance1
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.
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 \(\frac{79.1}{35.45}\).
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.
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.
Step 5: Compare the mole ratio to the given options and identify which empirical formula matches the ratio closest, confirming the correct formula is \(\mathrm{SiCl_4}\).
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