7g of a gas occupies a volume of 4:1 litre at 300K. If mol weight of gas is 42 , then find the pressure of it.
Answers
The molar mass of the gas is
126 g/mol
.
Explanation:
First calculate the moles of the gas using the gas law,
P
V
=
n
R
T
, where
n
is the moles and
R
is the gas constant. Then divide the given mass by the number of moles to get molar mass.
Calculate Moles
Given/Known
mass
:
0.950 g
pressure
:
P
=
0.985 atm
volume
:
V
=
232
mL
×
1
L
1000
mL
=
0.232 L
gas constant
:
R
=
0.082057338 L atm K
−
1
mol
−
1
temperature
:
T
=
95
o
C
+
273.15
=
368 K
Unknown
n
Equation
P
V
=
n
R
T
Solution
Rearrange the equation to isolate
n
and solve.
n
=
P
V
R
T
n
=
0.985
atm
×
0.232
L
0.082057338
L
atm
K
−
1
mol
−
1
×
368
K
=
0.007568 mol
(I'm keeping a couple of guard digits to reduce rounding errors. I'll round to three significant figures at the end.)
Molar Mass of Gas
Molar mass
=
grams
mol
Molar mass
=
0.950
g
0.007568
mol
=
126 g/mol