CHEMISTRY 11 AP – MOLECULAR FORMULA WORKSHEET
1) A compound has an empirical formula C5H11. If 0.0275 mol of the compound has a mass of 3.91 g,
what is the molecular formula of the compound?
N=Mdarma=
mass
142
=
empirical
2
=
"
1429k
£a=o?ffYstmoF
glmol
zxcsth
,
=
Ciotta
2) A gas has the empirical formula CH2. If 0.850 L of the gas at STP has a mass of 1.59 g, what is the
molecular formula?
N=mdarma=
mass
41.991mL
Emi
=
empirical
glmol
14.03
=3
.BG/mo1
-1%1=2
.BG/mol
9=16.04
7µmol
,=otg59fot×Pm4o=4t9$md
onto
z×c↳=aH6
3) A sample of gas has an empirical formula of O and has a molar mass that is 3 times that of CH4.
What is the molecular formula of the gas?
N=mdarma=
mass
48
=
3
empirical
glmol
×
3
48
=
MOT
3×0=03
4) A gas has an empirical formula CH. If 450.0 mL of the gas at STP has a mass of 0.522 g, what is
the molecular formula?
molar
N=
moot
empiric
.
26
mass
=
.
Oglmol
ftp.t#x,*x2I=26.og1moi2xCH=GHa
5) When a sample of nickel carbonyl is heated, 0.0600 mol of a gas containing carbon and oxygen is
formed. The gas has a mass of 1.68 g and is 42.9% C. What is the molecular formula of the gas?
N=mdarma=
mass
28.091mL
=
mFT=dj%§-mo ,
MOIC
42.9g
=
-28.091mA
×/m±=
57.19×4
mdO=
glmol
28.01
empirical
=L
1
empirical
mol
3.56875
=
1
CO
=
formula
1×0=0
3.56875
÷
6) A gas sample is analyzed and found to contain 33.0% Si and 67.0% F. If the gas density is 7.60 g/L
at STP, what is the molecular formula of the gas?
3.00g
1.7010291mL
33.09×401=1.1748
3.5720mA
7.2433mA
7.2433
12.01g
16.00g
28.09g
N=Mdarma=
mass
=
empirical
moot
glmol
85.09
=z
4%9-1,2*4=1.70×0 }/m0l
=
mol
empirical
0.986×102=0.986×28.029401--27.63
21.79×4%0*21.5278
3.52632mA
mol
's ,
MOI
1
=
formula
67.0g
F-
x
|qm0l_
=SiF3
=
÷
2xSiFz=
1.17438
Si2F6
7) A gas has the percentage composition: 78.3% B and 21.7% H. A sample bulb is filled with the
unknown gas and weighed. The mass of the unknown gas is found to be 0.986 times the mass of a
sample of nitrogen gas, N2 (g), in the same bulb under the same conditions of temperature and
pressure. What is the molecular formula of the unknown gas?
N=
=
empirical
mass
glmol
13.83
glmol
m9q=
molarmass_27.bg/mI=2
xlm0I=
1
mo1B=
MOIH
78.3g
empirical
formula
10.81g
md
-
÷
=
BH3
3
2xBHz=BaH6
8) A gas has the percentage composition: 30.4% N and 69.6% O. If the density of the gas is 4.11 g/L at
STP, what is the molecular formula of the gas?
MOIO
N=mdarma=
mass
=
empirical
46.01gal
2.1699
69.69×1,6%004=4.35
92.19101=2
*
=
94×2,264=92
.ly/mo1mo1N=3O.4gxlm0I=2.1699m0l
empirical Noa
I
formula
14.019
mol
=
÷
=
2
2×02=10204