The entropy changed involved in the conversion of 1 mole of liquid water at 373 K to vapour at the same temperature will be [ΔHvap=2.257kJ/gm] [MP PET 2002]

(1) 0.119 kJ

(2) 0.109 kJ

(3) 0.129 kJ

(4) 0.120 kJ

Subtopic:  Spontaneity & Entropy |
 74%
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When a liquid boils, there is [JIPMER 2002]

(1) An increase in entropy

(2) A decrease in entropy

(3) An increase in heat of vaporization

(4) An increase in free energy

Subtopic:  Spontaneity & Entropy |
 87%
From NCERT
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The work done to contract a gas in a cylinder, is 462 joules. 128 joule energy is evolved in the process. What will be the internal energy change in the process [MP PMT 2003]

(1) + 590 joules

(2) – 334 joules

(3) + 334 joules

(4) – 590 joules

Subtopic:  First Law of Thermodynamics |
 66%
From NCERT
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NEET 2023 - Target Batch - Aryan Raj Singh

For a carnot engine, the source is at 500 K and the sink at 300 K. What is efficiency of this engine

(1) 0.2

(2) 0.4

(3) 0.6

(4) 0.3

Subtopic:  Enthalpy & Internal energy |
 76%
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From Kirchhoff's equation which factor affects the heat of reaction [MP PMT 1990]

1. Pressure

2. Temperature

3. Volume

4. Molecularity

Subtopic:  Thermodynamics' Properties and process |
 76%
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The absolute enthalphy of neutralisation of the reaction MgO(s)+2HCl(aq)MgCl2(aq)+H2O(l) will be [CBSE PMT 2005]

(1) Less than –57.33 kJ mol–1

(2) –57.33 kJ mol–1

(3) Greater than –57.33 kJ mol–1

(4) 57.33 kJ mol–1

Subtopic:  Hess's Law |
 58%
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The heat of transition (ΔHt) of graphite into diamond would be, where

C(graphite)+O2(g)CO2(g);  ΔH=xkJ

C(diamond)+O2(g)CO2(g);  ΔH=ykJ [Pb. PET 1985]

(1) (x+y)kJmol1

(2) (xy)kJmol1

(3) (yx)kJmol1

(4) None of these

Subtopic:  Thermochemistry |
 76%
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Given that

2C(s)+2O2(g)2CO2(g);  ΔH=787kJ

H2(g)+12O2(g)H2O(l);  ΔH=286kJ

C2H2(g)+212O2(g)2CO2(g)+H2O(l);ΔH=1301kJ

Heat of formation of acetylene is

(1) –1802 kJ

(2) +1802 kJ

(3) –800 kJ

(4) +228 kJ

Subtopic:  Hess's Law |
 73%
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The enthalpy of combustion at 25°C of H2, cyclohexane (C6H12) and cyclohexene (C6H10) are –241, –3920 and –3800 KJ / mole respectively. The heat of hydrogenation of cyclohexene is

(1) – 121 KJ / mole

(2) + 121 KJ / mole

(3) – 242 KJ / mole

(4) + 242 KJ / mole

Subtopic:  Hess's Law |
 63%
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The heat change for the reaction H2 (g) +12O2 (g)H2O(l) is called

1. Heat of reaction

2. Heat of formation

3. Heat of vaporization

4. None of the above

Subtopic:  Thermochemistry |
 82%
From NCERT
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