Question

If a 8.5 g sample of an unknown compound decomposes to produce 7.29 g n 2 ​ o 5 ​ and 1.21 g h 2 ​ o, what is its empirical formula?

Answer 1

Answer is: empirical formula is HNO₃.
m(unknown compound) = 8,5 g.
m(N₂O₅) = 7,29 g.
m(H₂O) = 1,21 g.
n(N₂O₅) = m(N₂O₅) ÷ M(N₂O₅).
n(N₂O₅) = 7,29 g ÷ 108,01 g/mol.
n(N₂O₅) = 0,0674 mol.
n(H₂O) = m(H₂O) ÷ M(H₂O).
n(H₂O) = 1,21 g ÷ 18 g/mol.
n(H₂O) = 0,0673 mol.
n(H₂O) : n(N₂O₅) = 0,0673 mol : 0,0674 mol.
n(H₂O) : n(N₂O₅) = 1 : 1.
Compound has two hydroge, two nitrogen and six oxygen, can divided with two.