##C_4H_10##

Find the ##M_r## of the compound’s simplest formula a.k.a the empirical formula ##C_2H_5##

(12.01 x 2) + (1.01 x 5) = 29.07g/mol

The ##M_r## of the molecular formula is 60g/mol, therefore we have to divide 60 by 29.07.

##60/29.07## = 2 (integer)

Multiply the entire empirical formula of butane by 2 to find the molecular formula.

##C_2H_5## ##->## ##C_4H_10##