Question

If 20.50g of Sn combine completely with 24.49g of Cl to form a compound, what is the percent composition of tin in the compound? What is the empirical formula of the compound?

Answer 1

`"45.57% Sn"`

`"SnCl"_4`

Explanation:

The percent composition of tin in the compound will be equal to the ratio between the mass of tin and the mass of the compound, multiplied by `100`.

`color(blue)("% Sn" = m_(Sn)/m_"total" xx 100)`

Your initial sample of tine reacts completely with `"24.49 g"` of chlorine, which means that the total mass of the compound will be

`m_"total" = "20.50 g" + "24.49 g" = "44.99 g"`

The percent composition of tin in the compound will be

`(20.50 color(red)(cancel(color(black)("g"))))/(44.99color(red)(cancel(color(black)("g")))) xx 100 = color(green)("45.57% Sn")`

Now, to get the compound's empirical formula, use the molar masses of the two elements to determine how many moles of each you have in that sample

`20.50 color(red)(cancel(color(black)("g"))) * "1 mole Sn"/(118.71color(red)(cancel(color(black)("g")))) = "0.17269 moles Sn"`

`24.49 color(red)(cancel(color(black)("g"))) * "1 mole Cl"/(35.453 color(red)(cancel(color(black)("g")))) = "0.69077 moles Cl"`

Divide both values by the smallest one to get the mole ratio that exists between the two elements in the compound

`"For Sn: " (0.17269 color(red)(cancel(color(black)("moles"))))/(0.17269 color(red)(cancel(color(black)("moles")))) = 1`

`"For Cl: " (0.69077 color(red)(cancel(color(black)("moles"))))/(0.17269color(red)(cancel(color(black)("moles")))) ~~ 4`

The empirical formula of the compound, which tells you the smallest whole number ratio that exists between the two elements, will be

`"Sn"_1"Cl"_4 implies color(green)("SnCl"_4)`