Arkansas State University Department of Chemistry and Physics

1. Determine the empirical formula from the molecular formula:
 

a)  CH	h)  CH
b)  CH3	i)  Na2SO4
c)  C3H8	j)  C6H5N
d)  Fe(CO)3	k)  P2O5
e)  CH2O	l)  ReCl3
f)  NH2	m)  SeO3
g)  CaBr2	n)  LiCl

2.  Determine the empirical formula from the percent composition for each of the following:

a) 92.24 % C; 7.76 % H     => CH

b) 36.48 % Na; 25.44 % S; 38.08 % O    => Na₂SO₃

c)  49.99 % C; 5.61 % H; 44.40 % O    => C₃H₄O₂

d) A compound analyzes as 79.08 % C; 5.54 % H and 15.38 % N.  What is the molecular formula if the molar mass is 273.36 g/ mol? =>    C₁₈H₁₅N₃

e)  38.76 % Ca; 19.97 % P; 41.27 % O   => Ca₃P₂O₈; The compound is actually: Ca₃(PO₄)₂