A dead alkaline battery is found to contain a compound of manganese and oxygen. Its percentage composition is 70.0% Mn and 30.0% O. What is the empirical formula of this substance?

Empirical formula is Mn2O3

Explanation:

Mn = 70.0%

O = 30.0%

Mn = 54.93g/mol

O = 16g/mol

Assume

Mn = 70.0g

O = 30.0g

Mn = 70/54.93 = 1.27

O =   30/16 = 1.875

Divide each by the lower number of moles and round

Mn = 1.27/1.27 = 1

O =   1.875/1.27 = 1.476 so 1.5

Needs to be whole numbers so

Mn = 2

O = 3

Empirical formula is Mn2O3

"the periodic table is arranged in order of atomic number."