MEDIUM
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Assertion: Two metallic spheres of same size, one of copper and the other of aluminum, heated to the same temperature, will cool at the same rate when they are suspended in the same enclosure.

Reason: The rate of cooling of a body is directly proportional to the excess of temperature of the body over the surroundings.

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Important Questions on Thermodynamics

EASY
The work done during combustion of 9×10-2 kg of ethane, C2H6(g) at 300 K is (Given R=8.314 JK1mol1 , atomic mass C=12,H=1 )
HARD
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The above P-V diagram represents the thermodynamic cycle of an engine, operating with an ideal mono-atomic gas. The amount of heat, extracted from the source in a single cycle, is:
MEDIUM
A system consisting of 1 mol of an ideal gas undergoes a reversible process, ABCA (schematically indicated in the figure below). If the temperature at the starting point A is 300 K and the work done in the process BC is 1 L atm, the heat exchanged in the entire process in L atm is

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EASY
A gas undergoes change from state A to state B. In this process, the heat absorbed and work done by the gas is 5 J and 8 J, respectively. Now gas is brought back to A by another process during which 3 J of heat is evolved. In this reverse process of B to A.
MEDIUM
The qualitative sketches I, II and III given below show the variation of surface tension with molar concentration of three different aqueous solutions of KCl, CH3OH  and CH3CH211OSO3- Na+ at room temperature. The correct assignment of the sketches is -

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MEDIUM
X g of ice at 0oC is added to 340g of water at 20oC . The final temperature of the resultant mixture is 5oC . The value of X (in g) is closest to

[Heat of fusion of ice =333 J/g ; Specific heat of water =4.184 J/g.K ]
MEDIUM
A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of 3 7 . 0 C. As it does so, it absorbs 208 J of heat. The values of q and w for the process will be 
(R = 8.314 J/mol K) (ln7.5 = 2.01)
HARD
The volume vs. temperature graph of 1 mole of an ideal gas is given below

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The pressure of the gas (in atm) at X, Y and Z, respectively, are
HARD
An ideal gas undergoes isothermal compression from 5 m3 to 1 m3 against a constant external pressure of 4 N m-2. The heat released in this process is 24 J mol-1K-1 and is used to increase the pressure of 1 mole of Al. The temperature of Al increases by:
MEDIUM

The combination of plots which does not represent isothermal expansion of an ideal gas is

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EASY
An ideal gas undergoes isothermal expansion at constant pressure. During the process:
MEDIUM
n moles of an ideal gas undergoes a process AB as shown in the figure. The maximum temperature of the gas during the process will be:
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MEDIUM
For the isothermal reversible expansion of an ideal gas
EASY
Calculate the work done during compression of 2 mol of an ideal gas from a volume of 1m3 to 10 dm3 at 300 K against a pressure of 100 kPa.
MEDIUM
A gas is allowed to expand in a well-insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy ΔU of the gas in joules will be
MEDIUM
The molar enthalpy change for H2OlH2Og at 373 K and 1 atm is 40 kJ/mol . Assuming ideal behaviour, the internal energy change for vaporization of 1 mol of water at 373 K and 1 atm in kJ mol-1 is:
MEDIUM

The three processes in a thermodynamic cycle shown in the figure are : Process 12 is isothermal; Process 23 is isochoric (volume remains constant); Process 13 is adiabatic.

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The total work done by the ideal gas in this cycle is,10 J. The internal energy decreases by, 20 J in the isochoric process. The work done by the gas in the adiabatic process is, -20 J. The heat added to the system in the isothermal process is

HARD
A reversible cyclic process for an ideal gas is shown below. Here, P, V, and T are pressure, volume and temperature, respectively. The thermodynamic parameters q, w, H and U are heat, work, enthalpy and internal energy, respectively.

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The correct option(s) is (are)
EASY
A piece of ice falls from a height h so that it melts completely. Only one-quarter of the heat produced is absorbed by the ice and all energy of ice gets converted into heat during its fall. The value of h is:
(Latent heat of ice is 3.4×105J kg-1 and g=10N kg-1)
HARD
A closed tank has two compartments A and B, both filled with oxygen (assumed to be ideal gas). The partition separating the two compartments is fixed and is a perfect heat insulator (Figure1). If the old partition is replaced by a new partition which can slide and conduct heat but does not allow the gas to leak across (Figure 2), the volume (in m3) of the compartment A after the system attains equilibrium is 20x m3. Write the value of x.

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