Answer:
Explanation:
The trick here is to realize that if you know the volume of a gas at STP, you can use the fact that
1
mole of any ideal gas occupies
22.7 L
under STP conditions to calculate how many moles of gas you have in your sample.
Under STP conditions:
1 mole of an ideal gas = 22.7 L
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In your case, you know that your sample of gas occupies
2.28 L
under STP conditions, which are currently defined as a pressure of
100 kPa
and a temperature of
0
∘
C
.
This means that your sample will contain
2.28
L
⋅
molar volume of a gas at STP
1 mole gas
22.7
L
=
0.10044 moles gas
Now, the molar mass of the gas is the mass of exactly
1
mole of the gas. In your case, you know that you get
3.78 g
for every
0.10044
moles, which means that you have
1
mole
⋅
3.78 g
0.10044
moles
=
37.6 g
Since this is the mass of
1
mole of gas, you can say that the molar mass of the gas is
molar mass = 37.6 g mol
−
1
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