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5.0 g of nitrogen gas at 20°C and an initial pressure of
Chapter 17, Problem 56P(choose chapter or problem)
Problem 56P
5.0 g of nitrogen gas at 20°C and an initial pressure of 3.0 atm undergo an isobaric expansion until the volume has tripled.
a. What are the gas volume and temperature after the expansion?
b. How much heat energy is transferred to the gas to cause mis expansion?
The gas pressure is then decreased at constant volume until the original temperature is reached.
c. What is the gas pressure after the decrease?
d. What amount of heat energy is transferred from the gas as its pressure decreases?
e. Show the total process on a pV diagram. Provide an appropriate scale on both axes.
Questions & Answers
QUESTION:
Problem 56P
5.0 g of nitrogen gas at 20°C and an initial pressure of 3.0 atm undergo an isobaric expansion until the volume has tripled.
a. What are the gas volume and temperature after the expansion?
b. How much heat energy is transferred to the gas to cause mis expansion?
The gas pressure is then decreased at constant volume until the original temperature is reached.
c. What is the gas pressure after the decrease?
d. What amount of heat energy is transferred from the gas as its pressure decreases?
e. Show the total process on a pV diagram. Provide an appropriate scale on both axes.
ANSWER:
Step 1 of 5
a.) We need to find out the gas volume and temperature after the expansion.
From the ideal gas equation,
\(p_{1} V_{1}=n R T_{1}\)
Implies,
\(V_{1}=\frac{n R T_{1}}{p_{1}}\)
We know that,
\(n =\frac{M}{M_{m o l}}\)
\(n =\frac{5 g}{28 g / m o l}=0.1786 \mathrm{~mol}\)
The initial pressure is, \(p_{1}=3 a t m=304000 \mathrm{~Pa}\)
The initial temperature is, \(T_{1}=20^{0} \mathrm{C}=293 \mathrm{~K}\)
So,
\(V_{1}=\frac{(0.1786 \mathrm{~mol})(8.31 \mathrm{~J} / \mathrm{mol} \mathrm{K})(293 \mathrm{~K})}{304000 \mathrm{~Pa}}\)
The process is isobaric expansion that is \(p_{1}=p_{2}\)
So we can write,
\(\frac{V_{2}}{T_{2}}=\frac{V_{1}}{T_{1}}\)
The volume has tripled during the process.
That is \(V_{2}=3 V_{1}\)
So,
\(T_{2} =\frac{3 V_{1} T_{1}}{V_{1}}\)
\(T_{2} =3 T_{1}=3 \times 273 \mathrm{~K}\)
\(T_{2} =879 \mathrm{~K}\)