As is typical with these questions, we assume 100*g100⋅g of unknown compound, and work out the MOLAR quantities of each element present:
" moles of C": moles of C: (15.8*g)/(12.011*g*mol^-1)=1.32*mol15.8⋅g12.011⋅g⋅mol−1=1.32⋅mol
" moles of K": moles of K: (52.8*g)/(39.10*g*mol^-1)=1.35*mol52.8⋅g39.10⋅g⋅mol−1=1.35⋅mol
" moles of O": moles of O: (32.1*g)/(15.999*g*mol^-1)=2.00*mol32.1⋅g15.999⋅g⋅mol−1=2.00⋅mol
Now if we divide thru by the lowest molar quantity, we get CKO_(1.5)CKO1.5; if we multiply this preiminary formula by 22 we get whole numbers:
C_2K_2O_3C2K2O3 is the empirical formula.
But "(empirical formula)"xxn(empirical formula)×n == "molecular formula"molecular formula
Thus, solving for nn:
150.22*g*mol^-1=nxx(2xx12.011+2xx39.1+3xx15.999)*g*mol^-1150.22⋅g⋅mol−1=n×(2×12.011+2×39.1+3×15.999)⋅g⋅mol−1
Clearly, n=1n=1, and the molecular formula is C_2O_3K_2C2O3K2
This corresponds to no reasonable formula I know; C_2O_4K_2C2O4K2 would be reasonable. It is possible that you have been given duff values.
