Free NEET Chemistry multiple-choice questions on Entropy & Second Law. Attempt each question and reveal the answer with a full explanation.
The entropy change for the isobaric heating of 1 , mole of an ideal gas from temperature T 1 to T 2 is: C p (T 2/T 1) C v (T 2/T 1) R (T 2/T 1) C p (T 2 - T 1) In which of the following processes, the entropy decreases? N 2(g) + 3H 2(g) 2NH 3(g) I 2(s) I 2(g) Dissolution of NH 4Cl in water Expansion of an ideal gas Identify the correct relationship for an ideal gas in an adiabatic reversible expansion. TV -1 = constant T V = constant PV = constant PT = constant The Third Law of Thermodynamics helps in determining: Absolute entropy of a substance Enthalpy of a reaction Spontaneity of a reaction Internal energy of a gas Which of the following processes is associated with a decrease in entropy? Freezing of water to ice Dissolution of NH 4Cl in water Evaporation of a liquid Expansion of a gas at constant temperature In which case is the number of degrees of freedom for a monoatomic gas molecules? 3 5 6 2 In an isolated system, the change in entropy ( ΔS ) for a spontaneous process is: > 0 < 0 = 0 ≤ 0 The efficiency of a Carnot engine operating between 400 , K and 800 , K is: 0.5 0.75 0.25 1.0 Which of the following processes has S < 0 ? Freezing of liquid water to ice Sublimation of dry ice Dissolution of sugar in water Expansion of a gas into vacuum The absolute entropy of a perfectly crystalline substance at 0 , K is zero. This is a statement of: Third Law of Thermodynamics Second Law of Thermodynamics First Law of Thermodynamics Zeroth Law of Thermodynamics A process which proceeds of its own accord without any external assistance is called: Spontaneous process Non-spontaneous process Reversible process Adiabatic process For an adiabatic process involving an ideal gas, the relationship between T and V is given by TV x = constant . The value of x is: - 1 1 - 1/ For a spontaneous process, which of the following expressions involving the entropy of the system ( S sys ) and the entropy of the surroundings ( S surr ) must be true? S sys + S surr > 0 S sys + S surr = 0 S sys > 0 always S surr > 0 always Order the following substances in terms of increasing molar entropy at 298 , K : H 2O(s), H 2O(l), H 2O(g) . H 2O(s) < H 2O(l) < H 2O(g) H 2O(g) < H 2O(l) < H 2O(s) H 2O(l) < H 2O(s) < H 2O(g) H 2O(s) < H 2O(g) < H 2O(l) For which of the following processes is S system positive? Dissolution of sugar in water Freezing of liquid water Condensation of steam Compression of an ideal gas A Carnot engine operates between a source at 500 , K and a sink at 300 , K . The efficiency of the engine is: 40% 60% 20% 100% The absolute entropy of a substance 'X' at 298 , K is calculated using which law? Third Law of Thermodynamics First Law of Thermodynamics Second Law of Thermodynamics Zeroth Law of Thermodynamics In which of the following is the standard molar entropy of the substance the highest? O 2(g) at 298 , K O 2(l) at 90 , K O 2(s) at 50 , K H 2O(l) at 298 , K Which property of a system is defined by the Second Law of Thermodynamics? Entropy Enthalpy Internal Energy Temperature According to the Third Law of Thermodynamics, at 0 , K , the entropy of a perfectly crystalline substance is: Zero Maximum Infinite Positive Which of the following is the correct mathematical expression for the Second Law of Thermodynamics regarding the spontaneity of a process in an isolated system? S total > 0 S total < 0 G < 0 U = 0 According to the Third Law of Thermodynamics, which of the following has zero entropy at 0 K ? Perfectly crystalline substance Amorphous solid Gas at low pressure Liquid helium In a spontaneous process, the entropy of the universe: Always increases Always decreases Remains constant Increases only if the process is endothermic In which of the following cases does the entropy of the system decrease? Freezing of water Sublimation of iodine Dissolution of salt in water Expansion of gas The molar entropy of a substance is expected to be maximum in: Gaseous state Liquid state Solid state All states have equal entropy The values of H and S for the reaction, C(graphite) + CO 2(g) 2CO(g) are 170 kJ and 170 JK -1 respectively. This reaction will be spontaneous at - 510 K 710 K 910 K 1110 K Of the following, the largest value of entropy at 25°C and 1 atm is that of CH4 H2 C2H6 C2H2 In which case change in entropy is negative? 2H(g) -> H2(g) Evaporation of water Expansion of a gas at constant temperature Sublimation of solid to gas For the reaction 2Cl(g) Cl 2(g) , the correct signs of H and S are: "negative, negative" "positive, positive" "positive, negative" "negative, positive" The enthalpy of fusion of water is 6.01 , kJ , mol -1 . The entropy change for the melting of 1 , mol of ice at 0 ∘C is: 22.0 , J , K -1 , mol -1 10.5 , J , K -1 , mol -1 6.01 , J , K -1 , mol -1 0.022 , J , K -1 , mol -1 The entropy change for the surroundings when 1 , mol of H 2O(l) is formed under standard conditions ( H ∘ = -286 , kJ , mol -1 ) at 298 , K is: 959.7 , J , K -1 -959.7 , J , K -1 286 , J , K -1 1.04 , J , K -1 Consider the following graph of pressure versus volume for an ideal gas. Which path represents an adiabatic process? The steeper curve The shallower curve The horizontal line The vertical line For a sample of perfect gas when its pressure is changed isothermally from P i to P f , the entropy change is given by: S = nR (P i / P f) S = nR (P f / P i) S = nRT (P i / P f) S = RT (P i / P f) In which case is S positive? Sublimation of Iodine Freezing of water Condensation of a gas Reaction: N 2(g) + 3H 2(g) 2NH 3(g) If the enthalpy of vaporization of water is 186.5 , kJ , mol -1 , then the entropy of its vaporization will be: 0.5 , kJ , K -1 , mol -1 1.0 , kJ , K -1 , mol -1 1.5 , kJ , K -1 , mol -1 2.0 , kJ , K -1 , mol -1 The intensive property among the following is: Electromotive force ( E cell ) Heat capacity Entropy Volume Calculate the entropy change for the following reversible process: 1 mol of liquid water at 100 ∘ C converts to steam at 100 ∘ C . ( Δ vap H = 40.6 kJ mol -1 ) 108.8 J K -1 mol -1 406 J K -1 mol -1 0.406 J K -1 mol -1 10.88 J K -1 mol -1 During the adsorption of a gas on a solid surface, which of the following is correct? ΔH < 0, ΔS < 0 ΔH > 0, ΔS > 0 ΔH < 0, ΔS > 0 ΔH > 0, ΔS < 0 What is the entropy change ( ΔS ) when 1 mole of an ideal gas expands isothermally and reversibly from 10 L to 100 L at 300 K ? 19.14 J K -1 38.28 J K -1 8.314 J K -1 0 What is the change in entropy when 1 , mol of an ideal gas is heated from 300 , K to 600 , K at constant volume? ( C v = 1.5R ) 1.5R 2 R 2 2.5R 2 1.5R For an ideal gas, the slope of an adiabatic P-V curve is higher than the slope of an isothermal P-V curve by a factor of: - 1 1/ + 1 In which case does the entropy of the system increase? Adsorption of gas on charcoal Condensation of water vapor Thermal decomposition of CaCO 3(s) Formation of NH 3 from N 2 and H 2 Consider the following P-V diagram for an ideal gas starting from the same initial state. Which curve represents an isothermal expansion and which represents an adiabatic expansion? Curve A is isothermal, Curve B is adiabatic Curve A is adiabatic, Curve B is isothermal Both are isothermal but at different temperatures Both are adiabatic but with different gases Which of the following substances possesses a non-zero 'residual entropy' at 0 , K according to the exceptions of the Third Law of Thermodynamics? CO(s) Ag(s) Diamond(s) Hg(l) For a spontaneous process in an isolated system, the change in entropy ( S total ) must be: Positive Negative Zero Initially positive, then negative The entropy change ( S ) for the isothermal expansion of n moles of an ideal gas from an initial pressure P 1 to a final pressure P 2 is given by: S = nR (P 1/P 2) S = nR (P 2/P 1) S = nC p (P 1/P 2) S = RT (P 1/P 2) Which of the following is an intensive property? Standard electrode potential ( E ) Internal energy ( U ) Gibbs free energy ( G ) Mass ( m ) When water freezes to ice at 0 C and 1 , atm , which of the following is correct? S sys < 0 and S surr > 0 S sys > 0 and S surr < 0 S sys = 0 and S surr = 0 S sys < 0 and S surr < 0 According to Trouton's rule, the molar entropy of vaporization ( vap S ) for most non-associated liquids at their boiling point is approximately: 88 , J , K -1 , mol -1 44 , J , K -1 , mol -1 22 , J , K -1 , mol -1 110 , J , K -1 , mol -1 Which of the following molecules shows a non-zero residual entropy at 0 , K due to random orientation in the crystal lattice? CO CO 2 H 2O (ice) O 2 In a reversible adiabatic process for an ideal gas, the relationship between T and P is: T P 1- = constant T P -1 = constant T P = constant T P = constant A refrigerator works between 0 C and 30 C . Its coefficient of performance (COP) is approximately: 9.1 1.0 10.1 0.1 For which of the following processes is S surroundings always zero? Reversible adiabatic process Isothermal expansion Free expansion Isochoric heating For the expansion of a real gas into vacuum (Joule expansion), which of the following is true for the final temperature T f compared to initial T i ? T f < T i T f > T i T f = T i Depends on the gas type What is the entropy change when 1 , mol of an ideal gas is mixed with 1 , mol of the same ideal gas at the same T and P ? Zero R 2 2R 2 R 4 For the reaction N 2(g) + 3H 2(g) 2NH 3(g) , the value of S is expected to be: Negative Positive Zero Impossible to predict without values The expression for the efficiency of a Carnot engine in terms of heat absorbed ( q 2 ) and heat rejected ( q 1 ) is: = 1 + q 1 q 2 = 1 - q 1 q 2 = q 1 q 2 = q 2 - q 1 q 1 Which of the following statements is true for a reversible adiabatic process involving an ideal gas? PV = constant S = 0 q = 0 All of these The enthalpy change for the transition of liquid water to steam is 40.8 kJ/mol at 373 K . The entropy change for this process is: 109.4 J/K/mol 10.94 J/K/mol 408 J/K/mol 1.09 J/K/mol What is the relationship between the slope of an adiabatic P-V curve and an isothermal P-V curve for an ideal gas? Slope adi = Slope iso Slope iso = Slope adi Slope adi = Slope iso Slope adi = (1/ ) Slope iso The entropy of mixing for 1 , mole of an ideal gas A and 1 , mole of an ideal gas B at the same temperature and pressure is given by: 2R 2 R 2 2R 0.5 0 Which of the following molecules has a non-zero residual entropy at 0 , K due to orientation disorder? CO O 2 CO 2 Ne A refrigerator is used to transfer heat from a cold reservoir at 270 , K to a hot reservoir at 300 , K . The coefficient of performance (COP) is: 9 10 1 0.1 The change in entropy when 1 , mole of an ideal gas expands isothermally from 10 , atm to 1 , atm at 300 , K is: 19.15 , J , K -1 -19.15 , J , K -1 8.314 , J , K -1 2.303 , J , K -1 In a reversible process, the entropy change of the surroundings ( S surr ) is related to the heat exchanged ( -q rev ) at temperature T by: S surr = -q rev / T S surr = q rev / T S surr = 0 S surr = -q rev T According to the Boltzmann formula, the entropy of a system is related to the number of microstates ( W ) by S = k W . For a perfectly crystalline substance at absolute zero, W is: 1 0 Infinity Equal to the number of atoms The unit of the Clausius-Clapeyron constant L/T in the context of phase transitions is the same as the unit of: Entropy Enthalpy Gas Constant Heat Capacity The entropy change ( S ) for the conversion of 1 , mol of liquid water at 100 C to steam at the same temperature is 109 , J , K -1 , mol -1 . The heat absorbed by the system is: 40.66 , kJ 10.9 , kJ 373 , kJ 4.06 , kJ Which of the following statements is correct for the spontaneous adsorption of a gas ? S is negative and, therefore, H should be highly positive S is negative and therefore, H should be highly negative S is positive and, therefore, H should be negative S is positive and, therefore, H should also be highly positive For the reaction, 2Cl(g) -> Cl2(g) , the correct option is : r H > 0 and r S < 0 r H < 0 and r S > 0 r H < 0 and r S < 0 r H > 0 and r S > 0 For irreversible expansion of an ideal gas under isothermal condition, the correct option is: U 0, S total 0 U = 0, S total 0 U 0, S total = 0 U = 0, S total = 0 In which of the following processes entropy increases? A. A liquid evaporates to vapour. B. Temperature of a crystalline solid lowered from 130 K to 0 K. C. 2NaHCO3 (s) -> Na2CO3 (s) + CO2 (g) + H2O (g) D. Cl2 (g) -> 2Cl (g) Choose the correct answer from the options given below: A and C A, B and D A, C and D C and D During an isothermal expansion of a real gas into vacuum (Joule expansion), the temperature of the gas: Decreases Increases Remains constant First increases then decreases The entropy of mixing of 1 , mol of O 2 and 1 , mol of N 2 at the same temperature and pressure (assuming ideal behavior) is: R 4 R 2 2R 2 Zero Which of the following is the correct Clausius-Clapeyron equation for the liquid-vapor equilibrium? dP dT = vap H T(V g - V l) dP dT = vap H T V l dV dT = vap H P T dP dV = vap S T Which of the following processes is the basis for the definition of the Kelvin scale of temperature? Carnot cycle Joule-Thomson effect Phase transition of water Constant volume gas thermometer Which of the following Maxwell relations is correct for a system undergoing a reversible process? ( S V ) T = ( P T ) V ( S P ) T = ( V T ) P ( V S ) P = -( T P ) S ( P S ) V = ( T V ) S The value of S is negative for which of the following processes? Freezing of water Melting of ice Evaporation of water Expansion of gas at constant temperature Two moles of an ideal gas undergo free expansion from 10 L to 100 L at 300 K. The values of S system and S surroundings are (R is universal gas constant) S system = 0 ; S surroundings = 0 S system = 4.606 ,R ; S surroundings = -4.606 ,R S system = 0 ; S surroundings = 4.606 ,R S system = 4.606 ,R ; S surroundings = 0 Considering entropy ( S ) as a thermodynamic parameter, the criterion for the spontaneity of any process is: S system + S surroundings > 0 S system - S surroundings > 0 S system > 0 only S surroundings > 0 only