BasilP252viz
Answered

A compound of silicon and fluorine was analyzed and found to consist of 33.0% silicon and 67.0% fluorine by mass. The molecular mass of the compound was determined by experiment to be 170 g/mol. What is the molecular formula of the compound? (Si2F6)

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Kaiusviz
We first compute the no. of moles of each element in the compound. So first, the Si is said to have 33% by mass in the solution. So we solve: (0.33 g Si/1 g sol'n)(1 mol Si/28 g Si)(170 g sol'n/1 mol sol'n) = 2.00 moles of Si. Then next we solve for the moles of F. We follow the same procedure: (0.67 g F/1 g sol'n)(1 mol F/19 g F)(170 g sol'n/1 mol sol'n) = 5.99 or 6.00 moles of F. So we have Si2F6.