If you had 5.000 grams sample of Li3Po4, how much lithium would you have?

Answer 1

You can find the % by mass of Li in Li₃PO₄ and then determine grams of Li in 5.000 grams of the sample, or you can find moles of Li₃PO₄ represented by 5.000 grams and then moles of Li and finally grams of Li.

(1). % Li by mass:

3 Li x 6.941 g/Li = 20.823 g Li

1 P = 30.97 g

4 O = 4 x 15.99 = 63.96

Total = 115.753 g/mol

% Li = 20.823 / 115.753 = 0.1799 = 17.99%

5.000 g x 0.1799 = 0.8995 g Li

(2). moles Li₃PO₄ = 5.000 g x 1 mol/115.753 g = 0.04320 moles

moles Li = 0.04320 moles Li₃PO₄ x 3 mol Li/mole Li₃PO₄ = 0.1296 moles Li

mass Li = 0.1298 moles Li x 6.941 g/mol = 0.8995 g Li