Question

A substance is 27 % C and 73 % S. Which is the mass of carbon in 300. g of this substance?

Answer 1

Mass of Carbon will be 84 grams

Explanation:

1/ Convert % to gram
`27g C . (1mol C )/(12.011g)= 2.3 mol C`

`73g S . (1mol S)/(32.059g)= 2.3 mol S`

2/ Divide by least number of mol
`(2.3molC)/(2.3mol) = 1mol C` ; `(2.3molS)/(2.3mol) = 1 mol S`

CS is the empirical formula. You need to find the molecular formula.

`(300g)/(12.011+32.059)g` = 7
Multiply 7 to the empirical formula so you will get `C_7S_7`. This is your molecular formula.

=> `7 mol C . (12.011g C)/(1mol C) = 84`grams C in the substance

Answer 2

The mass of carbon is 91. g.

Explanation:

`"Mass of C" = 300. color(red)(cancel(color(black)("g substance"))) × "27 g C"/(100 color(red)(cancel(color(black)("g substance")))) = "91. g C"`