UNIT#05 THERMODYNAMICS Flashcards
The heat was given to a body, which raises its temperature by 1°C is _____.
Specific Heat
The thermal capacity of 40g of aluminium (specific heat 0.2 cal0g-1C-1) is _____.
8 cal0C-1
(Thermal capacity=mc)
80g of water at 30°C is poured on a large block of ice which is at 0°C. The mass of ice
30 g
Mud houses are cooler in summer and warmer in winter because;
Mud is a bad conductor of heat
The heat capacity of a substance is infinite. It means ____
No change in temprature
The change in internal energy, when a gas is cooled from 927°C to 27°C is?
75%
(U=mcΔT)
Two cylinders of equal size are filled with an equal amount of ideal diatomic gas at room temperature. Both the cylinders are fitted with pistons. In-cylinder A the piston is free to move, while in cylinder B the piston is fixed. When the same amount of heat is added to cylinder A raises by 20K. What will be the rise in the temperature of the gas in cylinder B?
28K
The relation for the 1st law of thermodynamics can be expressed as:
ΔQ = ΔU + ΔW
Examples of the first law of thermodynamics are;
➡Working on a bicycle pump
➡Brakes applied by an automobile
➡Human Metabolism
1st law of thermodynamics is a consequence of the conservation of:
Energy
Which statement about the first law of thermodynamics is correct?
The increase in the internal energy of a system equals the heating of the system minus the work done by the system
In a thermodynamic system working substance is an ideal gas, its internal energy is in the form of;
Kinetic Energy only
➡Adiabatic Process
(Ideal gas possesses only K.E)
In an ideal gas, the molecules possess?
Ony K.E
Which one is true for internal energy?
➡It is the sum of all forms of molecular energies of the system
➡It is proportional to translational K.E of the molecules
➡It is a state function of a system
If two systems X and Y are in thermal equilibrium. If X is heated at constant volume and Y is heated at constant pressure, and again finally maintained at thermal equilibrium, then heat given to the systems X and Y and internal energy U stored in the systems X and Y are;
➡Qx < Qy
➡Ux = Uy
The internal energy of a body is maximum when its temperature is;
273K
(Internal Energy ∝ Translational K.E ∝ Temperature
An ideal gas is pressed at a constant temperature,. Its internal energy
Remains the same
When 20J of work was done on the gas, 40J of heat energy was released. If the initial internal energy of the gas was 70J, what is the final internal energy?
50J
(Q = ΔU - W)
By rubbing the objects together, their internal energy;
Increases
The internal energy of an ideal gas depends upon only;
Temperature
If a system undergoes contraction of volume, then the work done by the system will be:
Negative
The work done in the isochoric process is;
Zero
(W=PΔV)
➡As volume is constant, so ΔV=0
Q
Work done by air when it expands from 50 litres to 150 litres at a constant pressure of 2 atm is;
2 x 10^4 J
The equation W = P(V2 -1 V1) represents work done by the gas in;
an expansion at constant pressure
Find the change in internal energy of the system when a system absorbs 2 kilocalories o heat and at the same time does 500 joules of work;
7900 J
(Q = W + ΔU)
A system is described in terms of thermodynamics variable;
➡Pressure
➡Temperature
➡Volume
The concept of temperature is related to;
Zeroth Law of thermodynamics
Which of the following statement is correct or any thermodynamic system?
➡The internal energy changes in all processes❌
➡The change in entropy can never be zero❌
➡Internal energy and entropy are state functions ✅
➡The work done in an adiabatic process is always zero❌
Thermodynamics is the study of the relationship between;
Heat & other forms of energy
Heat added at a constant volume of a gas is used to:
To increase its internal energy
When heat is given to gas is an isobaric process then;
➡The work is done by the gas
➡Internal Energy of the gas increases
If the volume of a gas is decreased by 10% during the isothermal process then its pressure will:
Increase by 11.11%
During this process the volume of the system remains constant:
Isochoric
A gas does 10J of external work in an adiabatic process while expanding, then the change in internal energy is;
-10 J
(Q = ΔU + W)
During the adiabatic expansion of 2 moles of a gas, the internal energy of the gas is found to decrease by 2 joules, the work done during the process on the gas will be equal to;
2J
(Q = ΔU + W)
Starting with the same initial conditions, an ideal gas expands from volume V1 to V2 in three different ways. The work done by the gas is W1 if the process is purely isothermal. W2 if purely isobaric and W3 if purely adiabatic then;
W2>W1>W3
Cp - Cv value, find if 3 moels of gas give:
3R
A valid unit of specific heat capacity is;
Jkg-1K-1
If 1 mole of monoatomic gas γ=5/3 is mixed with 1 mole of diatomic gas γ=7/5. What is the value of γ for the mxiture?
1.5
Find the internal energy of the system containing 2 moles of oxygen and 4 moles of argon:
11RT
If the energy required to raise the temperature of 10°C is 20J at constant volume then how much energy is required to raise the same temperature at constant pressure?
40 J
Find the molar-specific heat capacity of diatomic gas which work done is Q/4 if heat is given to the system>
10/3 R
The internal energy of one gram of helium at 100K and one atmospheric pressure is;
300J
310 J of heat is required to raise the temperature of 2 moels of an ideal gas at constant pressure from 25°C to 35°C. The amount of heat energy required to raise the temperature of gas through the same range at constant volume is:
143J
The first law of thermodynamics is related to:
Law of conservation of energy
Cv/ Cp is equal to:
1/γ
When Cp = 20 J/kg k and 1 mole of gas is present then Cv is?
4.36 J/kgk
1 gamma for poly atomic gas is;
1.29
Which one is true about Cv and Cp?
Cp > Cv
Which of the following is incorrect?
➡Cp - Cv = R❌
➡Cp = R - Cv❌
➡Cp/Cv = R✅
➡ R + Cp = Cv❌
If the pressure of diatomic gas varies as P = aV2 then its heat capacity will:
17 R/6
Specific heat capacity in terms of heat capacity is;
C/m
At 0° K which of the following properties of gas will be zero
Kinetic Energy
What will be changed in internal energy when work is done by the system is 50KJ heat absorbed is 40 KJ
-10KJ
Gas laws are applicable to:
Gases alone and not to vapours
An ideal gas as compared to a real gas at very high pressure occupies:
More volume
The unit of pressure in the S.I Unit is
Pascal
Thermodynamics does not consider:
Time Factor
A system which can neither exchange matter nor energy with the surroundings is called:
Isolated system
Absolute zero temperature is taken as;
-273°C
In the isothermal process:
Temperature is constant
Absolute zero pressure will be;
When molecule moment o system is zero
If the volume of a gas is held constant and we increase its temperature then:
Its pressure rises
For a gas obeying Boyles’s law, if the pressure is doubled the volume becomes:
One half
If Cp = 34.4 J/mol K and the value of R is 8.314 then:
Cv = 26.1 J/mol K
The difference between the principal specific heats of nitrogen is 300 J/kg-K and the ratio of the two specific heats is 1.4 then:
Cp = 1050 J/kg-K
The equation of state corresponding to 8 g of O2 is:
PV = RT/4
Cv of gas is 8 calK-1mole-1. Find Cp/Cv. Assume R = 2calK-1mol-1
1.25
100g of water is heated from 30°C to 50°C. Ignoring the slight expansion of the water, the change in its internal energy is:
(specific heat of water is 4184 J kg-1 K-1)
8.4 kJ
When an ideal diatomic gas is heated at constant pressure, the fraction of the heat energy supplied that increases the internal energy of the gas is:
5/7
How much heat is needed to raise the temperature of 100 g of H2O from 22°C to 98°C?
32 kJ
A 500-gram cube of lead is heated from 25°C to 75°C. How much energy was required to heat the lead? The specific heat of lead is 0.129 J/g°C
3225 J
A closed container contains an ideal gas. Which of the following changes will result in a decrease in temperature?
➡Volume increase
➡Temperture decrease
The efficiency of the heat engine can be defined as:
1 - Q2/Q1
For an isothermal process, the first law of thermodynamics can be written as:
Heat absorbed = work done by the system
Boltzmann’s constant k is defined as:
R/N A
A liquid has mass m and specific heat capacity c. The rate of change in temperature of the liquid is R. What is the rate at which heat is transferred from the liquid?
Rmc
100W heater is used to heat 500g of water from 20°C to 50°C. How long should the heater be switched on?
The specific heat capacity of water is 4.2 J/gC
630 sec
The energy input to an engine is 60 J, and the work it performs is 15J. What is its thermal efficiency?
0.25
Which of the following is equivalent to a temperature of 150K?
-123°C
A monoatomic ideal gas is thermally insulated, so no heat can flow between it and its surroundings. Is it possible for the temperature of the gas to rise?
Yes
➡The temperature can rise if work is done on the gas
Some ice, at its melting point, is added to m kg of water at an initial temperature of 290K. if c is the specific heat capacity o water and L is the latent heat of fusion of ice. Ice melts completely. The final temperature of the water is 273 K. What is the minimum mass of ice that is required?
17 mc/L
Under what conditions of temperature and pressure do a real gas approximate to an ideal gas?
➡Pressure Low
➡Temperatre High
In which process the net work done is zero>
Isochoric
Internal energy remains the same throughout the process in:
Isothermal Process
An ideal gas is compressed to half of its initial volume. Which of these processes would result in maximum work done>
Adiabatic
If the system changes from a state P1 V1 to P2V2 by two paths then the quantity which remains unchanged is:
ΔQ -ΔW
An ideal reversible heat engine is 1 efficient only if:
The cold reservoir is at 0K
The efficiency of the heat engine in terms of temeprature of reservoir and sink is defined as:
1 - T1/T2
According to the first law of thermodynamics;
ΔQ = ΔU + ΔW
Which of the following is a thermodynamic coordinate?
R
When heat is given to the isobaric process then;
➡Work is done by the gas
➡Internal Energy of gas decreases
If N is the number of molecules of gas in a container. Then a number of moles can be calculated as:
N + NA
100 W heater is used to melt 50g of ice at 0°C. How long should the heater switch on?
Specific heat latent heat of fusion of ice is 334 J/g.
16.7 min
The sum of all forms of molecular energies (kinetic and potential) of a substance is termed as its:
Potential Energy
When an ideal gas of constant mass is heated in a container of fixed volume. What is the reason for the increase in pressure of the gas?
Average force per impact at the container wall increases
The isothermal process can be defined as:
PV = Constant
Which of the following process is irreversible?
A chemical explosion
During an adiabatic process, the pressure of the gas is found to be proportional to the fourth power of temperature. The ideal gas would be;
CH2
Temperature is defined by:
Zeroth Law of thermodynamics
The internal energy of the system depends on:
The path from the initial to the final state
The initial mass of water, at its boiling point, is 0.8 kg. 4 kW of the heater is used to boil it completely. Assuming the specific latent heat of vaporization of water in 2MJ/kg. What is the time taken to vaporize all the water?
400sec
100 W heater is used for 5 minutes to heat 500g of water. What is the change in the temperature of the water which is heated?
The specific heat capacity of water is 4.2 J/gC
14°C
100 W heater is used for 5 minutes to heat some water from 20°C to 50°C. What is the mass of water which is heated?
The specific heat capacity of water is 4.2 J/gC
240 g
A car of mass M is moving with speed v. The brake of mass m and specific heat capacity c is used to stop the car. If half of the kinetic energy of the car is absorbed by the brake, then what is the increase in temperature of the brake:
Mv2/4mc
If ΔU and ΔW represent internal energy and work done which is true?
ΔU = -ΔW in an adiabaic process
The P-V diagram of a diatomic gas is a straight line passing through the origin. What is the molar heat capacity of the gas in the process?
3R
What does the constant n represent in the equation of state for an ideal gas PV nRT?
Number of moles of the gas
If P=Po and V=Vo gas expands isothermally to P=3Po, then the volume is;
Vo/3
Which of the terms is related to thermodynamics?
➡System
➡Boudnary
➡Surrounding
The amount of heat supplied to 0.02 kg of nitrogen to raise its temperature by 45° is;
934J
What is the internal energy change in a system that has absorbed 800J of heat and work done is 500J?
300J
“The heat required to raise the temperature of one mole of the substance through 1K” is called:
Molar specific heat
Which of the following is not an assumption o the kinetic model of an ideal gas?
➡Collisions between molecules and walls of the container are elastic❌
➡The duration of collision between molecules is very short❌
➡All particles of gas have the same speed✅
➡All particles of gas have same mass❌
The thermodynamics process during which the pressure is kept constant, is called;
Isobaric
An ideal gas has a volume of 20ml, a temperature of 10°C and pressure of 100kPa. The volume of the gas is reduced to 10ml and the temperature is raised to 20°C. What is the new pressure of the gas?
207 kPa
Two identical gases expand i) isothermally ii) adiabatically. Work done is more in:
Isothermal Process
In which of the following processes the heat is neither absorbed nor released by a system?
Adiabatic
A heater is used for 5 minutes to heat 500g of water from 20°C to 50°C. What is the power of the heater?
The specific heat capacity of water is 4.2 J/gC
1260 W
Which of the following is equivalent to a temperature -50°C?
223K
In Boyle’s Law, which quantity is constant
T
A gas expands from V1 to V2. The amount of work done is greatest in:
Isobaric
If heat given is 6kcal and work done is 6kJ, then internal energy is;
19.1 kJ
A container is filled with oxygen and helium at the same temperature. The molar mass of oxygen is 32 g/mol and that of helium is 4 g/mol. What is the ratio:
average speed o oxygen molecules _______ average speed o helium molecules?
1/√8
How much energy is required to raise the temperature of 5.00 kg of lead from 20.0°C to its melting point of 327°C? The specific heat of lead is 128 J/kg°C
1.96 x 10^5 J
In thermodynamics first law is related with;
Energy conservation
In the VT diagram slope of the curve is:
nR/P
