CHEMISTRY 11 – 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
mdarmate
=
empirical
=
mass
ohatffthstmoi
'
14291mL
a .org/mo1=2
"
429k
zxcsth
,
-
Cotton
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?
molar
N=
onto
gtnol
41.9
mass
empir#=
Tyk
=3
,=ots5aI×¥=" " $md
}×c↳=a
.
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=mdarm=
mass
=
empirical
9
=
16
.
Oglmol
C8.Ogk#
16.0
×
3
=3
glmol
48.0 glmol
=
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?
N=
moot
molar
mass
empir#=
26
.
Oglmol
13¥
-
2
,=gj?o?o2t×,¥s×¥bY=2£og1m
×CH=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?
=mdarm=
N
empirical
28.091M¥
=
=L
28.05mg
mass
ftp.jbs#mo,=28.og/mo1molC=42.9gx/mI=3.575mo1
I
empirical
12.09
mdo
57.19×4
=
=
3.56875 mol
16.0g
formula
/
CO
=
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?
N=Mdarm=
mass
1.70×102941
=
ootm
mol 's
MOI
,
36<09-1%4
,l=
-
33
=
.0gx¥?↳=
.ly/mo1=2
85
empirical
hoxosglmol
1.17438mA
1
empirical
formula
3
F=6?0gx ftp.#=3.S2632m0l
÷l
.
Sitz
=
2×SiF3=
17438
Siztz
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=mdarm=
mass
empirical
=
27.bg/mI
13.8501=2
0.986×102--0.986×28.0501=27
.bg/mo1mo1B=78.3gxfy.ng0gL=7.25m0l
M£0
=
,
1
mol
H
-
21.7g
I
x
,?o÷=
21.7mm
-
7.25
empirical
formula
=
Btb
2×BHz=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?
N
=mdarm=
92.41
=
2
69.6g
MOIO
empirical
mass
=
46.0501
*
1--94×32.5=92
.ly/mo1mo1N=3O.4gxlm0L=2.m4m01
I
14.0g
=
×
1M¥
16.0g
4.35 mol
÷
2.1714
empirical
formula
=
Noa
2
2xN02=N204