As with all problems of this type, we assume a 100*g100⋅g mass of compound, and we determine the molar composition with respect to each element:
And thus:
"Moles of carbon"Moles of carbon == (74.0*g)/(12.011*g*mol^-1)74.0⋅g12.011⋅g⋅mol−1 == 6.16*mol6.16⋅mol
"Moles of hydrogen"Moles of hydrogen == (7.4*g)/(1.00794*g*mol^-1)7.4⋅g1.00794⋅g⋅mol−1 == 7.34*mol7.34⋅mol
"Moles of nitrogen"Moles of nitrogen == (8.6*g)/(14.01*g*mol^-1)8.6⋅g14.01⋅g⋅mol−1 == 0.614*mol0.614⋅mol
"Moles of oxygen"Moles of oxygen == (10.0*g)/(16.00*g*mol^-1)10.0⋅g16.00⋅g⋅mol−1 == 0.625*mol0.625⋅mol
So we have the molar composition. We simply divide thru by the smallest molar quantity to gets our empirical formula:
Dividing thru by 0.614*mol0.614⋅mol we get C_10H_12NOC10H12NO (clearly, I have done some rounding off!), as the empirical formula.
