.30 g of a volatile liquid displaces 90 cm^3 of air at STP in the victor mayer method the molecular mass of the liquid
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Answer:
We can use the Ideal Gas Law to solve this problem:.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
∣
∣
a
a
p
V
=
n
R
T
a
a
∣
∣
−−−−−−−−−−−−−−−
Since
n
=
m
M
, we can rearrange this equation to get
p
V
=
(
m
M
)
R
T
And we can solve this equation to get
M
=
m
R
T
p
V
STP is defined as 1 bar and 0 °C.
In your problem,
m
=
0.2 g
R
=
0.083 14 bar⋅L⋅K
-1
mol
-1
T
=
273.15 K
p
=
1 bar
V
=
56 mL
=
0.056 L
∴
M
=
0.2 g
×
0.083 14
bar⋅L⋅K
-1
mol
-1
×
273.15
K
1
bar
×
0.056
L
=
80 g/mol
∴ The molar mass of the compound is 80 g/mol, so the molecular mass is 80 u.
Note: The answer can have only one significant figure, because that is all you gave for the mass of the compound.
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