Question

A sample of a certain binary compound contains 6.93 g of silicon and 7.89 g of oxygen. What is the percent composition of the compound?

Answer 1

Given, mass of the silicon = 6.93 g

mass of the oxygen = 7.89 g

Calculate the number of moles of both atoms:

$Number of moles = \frac{given mass}{molar mass}$

Insert the given values of mass in above formula:

$Number of moles of silicon = \frac{given mass of silicon in g}{molar mass of silicon}$

= $\frac{6.93 g}{28 g/mol}$

= $0.2475 mol$

$Number of moles of oxygen = \frac{given mass of silicon in g}{molar mass of silicon}$

= $\frac{7.89 g}{16 g/mol}$

= $0.493125 mol$

Thus,

Total number of moles =  number of silicon+ number of mole of oxygen

= $0.493125 mol+0.2475 mol$ =$0.740625 mol$

$Percentage composition = \frac{number of moles of an atom}{total number of moles of the compound}\times 100$

Put the values in above formula:

$Percentage composition of silicon= \frac{number of moles of silicon}{total number of moles of the compound}\times 100$

$Percentage composition of silicon= \frac{0.2475 mol}{0.740625 mol}\times 100$

= $33.41 percent$

$Percentage composition of oxygen= \frac{number of moles of oxygen}{total number of moles of the compound}\times 100$

$Percentage composition of silicon= \frac{0.493125 mol}{0.740625 mol}\times 100$

= $66. 58 percent$

Thus, percent composition of silicon and oxygen is $33.41 percent$and $66. 58 percent$

Answer 2

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