According to the law, a perfect crystal's entropy is 0 at absolute zero, which is:

1. The first law               

2. Second law

3. Third law             

4. None of the above

Subtopic:  Spontaneity & Entropy |
 60%
From NCERT
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NEET 2023 - Target Batch - Aryan Raj Singh
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At constant pressure and temperature, the direction of any chemical reaction is one where the...... decrease.

1. Entropy               

2. Enthalpy

3. Gibbs energy       

4. None of the above

Subtopic:  Spontaneity & Entropy |
 55%
From NCERT
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The work done by a mass less piston in causing an expansion V (at constant temperature), when the opposing pressure, P is variable, is given by:

1. W= -PV               

2. W=0

3. W= -PV                     

4. none of these

Subtopic:  2nd & 3rd Law of Thermodynamics |
 65%
From NCERT
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Entropy decreases during:

1. crystallization of sucrose from solution

2. rusting of iron

3. melting of ice

4. vaporization of camphor

Subtopic:  Spontaneity & Entropy |
 72%
From NCERT
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Entropy change of vaporization at constant pressure is given by:

1. S(p)= HpT

2. S(v)=UvT

3. S(v)= HvP

4. None of the above

Subtopic:  Spontaneity & Entropy |
 75%
From NCERT
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What is the entropy change for the reaction given below, 

2H2 (g) + O2 (g) 2H2O(l)

at temperature 300 K? Standard entropies of H2 (g), O2(g) and H2O(l) are 126.6, 201.20 and 68.0 JK-1mol-1 respectively.

1. -318.4 JK-1mol-1                           .

2. 318.4 JK-1mol-1 

3. 31.84 JK-1mol-1                             

4. none of these

Subtopic:  Spontaneity & Entropy |
 72%
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If S° for H2, Cl2 and HCl are 0.13, 0.22 and 0.19 kJ K-1mol-1 respectively. The total change in standard entropy for the reaction, H2 + Cl2 2HCl is:

1. 30 J K-1mol-1                         

2. 40 J K-1mol-1

3. 60 J K-1mol-1                         

4. 20 J K-1mol-1

Subtopic:  Spontaneity & Entropy |
 80%
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The direct conversion of A to B is difficult and thus it is converted by path ACDB. Given

SAC=50 e.u; SCD=30 e.u; SBD=20 e.u.

(Where e.u. is the entropy unit)
then SAB would be:

1. +60 e.u                                       

2. +100 e.u

3. -60 e.u                                       

4. -100 e.u

Subtopic:  Hess's Law |
 60%
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In a flask, colourless N2O4(g) is in equilibrium with brown coloured NO2(g). At equilibrium when the flask is heated to 100°C, the brown colour deepens and on cooling it becomes less coloured. Which statement is incorrect about this observation?

1. The H for the reaction N2O4(g) 2NO2(g) is +ve

2. Paramagnetism increases on heating

3. The H-U at 100°C is equal to 200 cal

4. Dimerisation is reduced on heating

Subtopic:  First Law of Thermodynamics |
From NCERT
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Enthalpy of the reaction,

CH4(g) + 1/2O2(g) → CH3OH(l), is negative. If the enthalpy of combustion of CH4 and CH3OH are x and y respectively, then
which relation is correct?                                 

1. x>y         

2. x<y         

3. x=y           

4. xy

Subtopic:  Enthalpy & Internal energy |
From NCERT
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