2420 J 4850 J 1220 J 2280 J 485 J As described by the first law of thermodynamic

Question

2420 J
4850 J
1220 J
2280 J
485 J

As described by the first law of thermodynamics, the change in internal energy of a system is equal to _____.

the sum of the heat added and work performed
the product of the pressure and change in volume
the ratio of the heat added to the work performed
the difference between the heat added and work performed

6. A compression at a constant pressure of 20 kPa is performed on 9.0 moles of an ideal monatomic gas The compression reduces the volume of the gas from to What is the change in the internal energy of the gas? Let the ideal-gas constant R = 8.314 J/(mol • K).

4.2 kJ
-4.2 kJ
7.0 kJ
zero
-7.k

7. An ideal gas changes from a state defined by pressure p1 and volume V1 to a state defined by pressure p2 and volume V2. Which set of properties is independent of the path between the two states?

heat transfered to or from the gas
change in internal energy of the gas
work performed by or on the gas
work and heat transfer involving the gas


8. An ideal gas is carried around the cyclic process described by the diagram. Let and liters. How much work does the gas do in one cycle?

Explanation / Answer

1)

PV = nRT
where
P = 400 kPA
n = 20
T = 450 K

V = nRT/P = 20 * 8.314 * 450 / 400 = 187 L

now you can use:

V1/T1 = V2/T2 and solve for V2

V2 = V1 (T2/T1) = 187 x 320 / 450 = 133 L

It is not one of the given options but I can see no problems with the maths so I don't know what else to do.

5)

the relevant expression for the temperature volume relationship in an adiabatic expansion is

T V^(g-1) = cst

where g represents gamma = 5/3

in this case, T V^(2/3)= cst

therefore, 273.15 * (10)^(2/3) = T * (10.4)^(2/3) where T is the temperature after the expansion

solving for T:

T = 273.15* (10/10.4)^(2/3) = 266.1K = - 7.08C

7)

Work is the area under the line, so the route (whether it is a curve or straight line) will affect Work - this rules out C and D
I am inclined to say B, because internal energy is a measure of the condition of the gas regardless of how it got to that condition, where heat transfer seems to be more linked to work

9)

As described by the first law of thermodynamics, the change in internal energy of a system is equal to the difference between the heat added and work performed

Related Questions

Navigate

• Browse (All)
• Browse 2
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.