thermo sheet 1(sep2015)

8/18/2019 Thermo Sheet 1(Sep2015)

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Sheet- 1

Thermodynamics221PHYS

Pb01: An m1 = 485-gram brass block sits in boiling water (T1 = 100 C). It is taken out of

the boiling water and placed in a cup containing m2 = 485 grams of ice water (T2 = 0 C).

What is the final temperature, TF, of the system (i.e., when the two objects have the same T)?

(c brass = 380 J/kg.K; cwater = 4184 J/kg.K)

a. TF < 50 C b. TF = 50 C c. TF > 50 C

Pb02: You have two containers of water. The first container has 200 g of water at 80oC

and the second container has 200 g of water at 20oC. If the water in the two containers is

mixed, what would the equilibrium temperature be for this mixture?

(a) T > 80 °C (b) T 80 °C (c) T 50 °C

(d) T 20 °C (e) T < 20 °CPb03: You have two containers of water. The first container has 200 g of water at 80oC and

the second container has 100 g of water at 20oC. If the water in the two containers is mixed,

what would the equilibrium temperature be for this mixture?

(a) 50 °C ≤ T ≤ 80 °C (b) 20 °C ≤ T ≤ 50 °C (c) T 10 °C

(d) T < 10 °C



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Pb04: The process shown on the Pressure-Volume diagram is an

(A) adiabatic expansion. (B) isothermal expansion.

(C) isometric expansion. (D) isobaric expansion.

P

Vo

Pb05: In an isochoric process, there is no change in

(A) pressure. (B) temperature. (C) volume. (D) internal energy.

Pb06: The process shown on the Temperature-Volume graph is an

(A) adiabatic compression. (B) isothermal compression.

(C) isochoric compression. (D) isobaric compression.

T

Vo

Pb07: When the first law of thermodynamics, Q = ΔU + W, is applied to an

ideal gas that is taken through an isothermal process,

(A) ΔU = 0 (B) W = 0 (C) Q = 0 (D) none of the above

Pb08: An ideal gas is compressed to one-half its original volume during an isothermal

process. The final pressure of the gas

(A) increases to twice its original value. (B) increases to less than twice its original value.

(C) increases to more than twice its original value. (D) does not change.

Pb09: When the first law of thermodynamics, Q = ΔU + W, is applied to an

ideal gas that is taken through an adiabatic process,

(A) ΔU = 0. (B) W = 0. (C) Q = 0. (D) none of the above



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Pb10: A gas is taken through the cycle illustrated here.

During one cycle, how much work is done by an engine

operating on this cycle?

(A)PV (B) 2PV

(B) (C) 3PV (D) 4PV

P

2P

V 2V 3V 4V

Pb14 : Suppose that an ideal gas expands adiabatically. Does the temperature

(A) Increase (B) Decrease (C) Remain the same

Pb15: Two cylinders at the same temperature contain the same gas. If B has twice the volume

and half the number of moles as A, how does the pressure in B compare with the pressure in A?

(A) PB = 1/2 PA (B) PB = 2 PA (C) PB = 1/4 PA

(D) PB = 4 PA (E) PB = PA

Pb17 :A gas cylinder and piston are covered with heavy

insulation. The piston is pushed into the cylinder,

compressing the gas. In this process, the gas temperature

(A) doesn’t change. (B) decreases.

(C) increases. (D) there’s not sufficient information to tell.

Pb16: During an isothermal process, 5.0 J of heat is removed from an ideal gas. What is

the change in internal energy?

A) zero B) 2.5 J C) 5.0 J D) 10 J



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Pb19: The Speed of Molecules in Air

Air is primarily a mixture of nitrogen N2 molecules (molecular mass 28.0 u) and oxygen O2

molecules (molecular mass 32.0 u). Assume that each behaves as an ideal gas and determine

the rms speeds of the nitrogen and oxygen molecules when the temperature of the air is 293K.

Pb20: A container of an ideal gas has a moveable top. The top has an

area of 0.01 m2 and is 50 cm above the bottom of the cylinder. A

mass of 200 kg is placed on the container, which compresses the gas

by 20 cm. The gas in the container is initially at atmospheric pressure(1.01 x 105 Pa) and 20oC. What is the new temperature of the gas?

Pb18: If sulfur dioxide were an “ideal” gas, the pressure at 0°C exerted by 1.000 mol

occupying 22.41 L would be 1.000 atm. Use the van der Waals equation to estimate the

“real” pressure.

R= 0.0821 L.

atm/mol.

KT = 273.2 K

V = 22.41 L

a = 6.865 L2.

atm/mol2

b = 0.05679 L/mol

Pb21: A sample of gas expands from 1.0 m3 to 4.0m3 while its pressure decreases from 40 Pa to 10Pa. How much work is done by the gas if its

pressure changes with volume via each of the three paths shown in the Figure below?

Pb22: A cylinder of radius 5 cm is kept at pressure with a piston

of mass 75 kg.

a) What is the pressure inside the cylinder? b) If the gas expands such that the

cylinder rises 12.0 cm, what work was done by the gas?

c) What amount of the work went into changing the

gravitational PE of the piston?

d) Where did the rest of the work go?



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Pb23: from the figure answer the following:

a) What amount of work is performed by the gas in the cycle IAFI?

b) How much heat was inserted into the gas in the cycle IAFI?

c) What amount of work is performed by the gas in the cycle IBFI?

V (m3)

Pb24: Imagine that we rapidly compress a sample of air whose initial pressure is

105 Pa and temperature is 220C (= 295 K) to a volume that is a quarter of its

original volume (e.g., pumping bike’s tire). What is its final temperature?

Pb25: An ideal gas with = 1.4 occupies 4.0 L at 300 K & 100

kPa pressure. It’s compressed adiabatically to ¼ of original

volume, then cooled at constant V back to 300 K, & finally

allowed to expand isothermally to its original V . How muchwork is done on the gas?

Pb26: A thermodynamic system undergoes a process in which its internal energy decreases

by 465 J. Over the same time interval, 236 J of work is done on the system. Find the energy

transferred from it by heat.

Pb27: Fuel ignites in a diesel engine from the heat of compression

(no spark plug needed). Compression is fast enough to be adiabatic.

If the ignit temperature is 500C, what compression ratio Vmax /

Vmin is needed? Air’s specific heat ratio is = 1.4, & before the

compression the air is at 20 C.

Pb28: A 2.20-mol sample of helium gas initially at 300 K, and 0.400 atm is compressed

isothermally to 1.80 atm. Note that the helium behaves as an ideal gas.

(a) Find the final volume of the gas.

(b) Find the work done on the gas.

(c) Find the energy transferred by heat.



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Pb29: A 10 kg of ice at 0oC is dropped into a steam chamber at 100oC. How much steam

is converted to water at 100oC?

Pb30: from the kinetic theory of gases drive the ideal gas equation?

nRT PV

Pb31: For an ideal gas in an adiabatic process , show that

Pb32: For an ideal gas and using the concept of Enthalpy,

show that the specific heats at constant pressure and constant

volume are related by

P V C C R

thermo sheet 1(sep2015)

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