NCERT Class 11 Chemistry Chapter 6 Chemical Thermodynamics Very Short Question And Answers

NCERT Class 11 Chemistry Chapter 6 Chemical Thermodynamics Very Short Question Answers

Question 1. Which type of system does not interact with its surroundings? Classify the following systems into open, closed, and isolated systems: a plant certain amount of a liquid enclosed in a container with rigid, impermeable, and adiabatic wall
Answer:

1. Isolated System
2. Open
3. Isolated

Question 2. If the volume and density of 5g of pure iron sample are ‘ V’ and ‘ d.’ respectively then what will be the volume and density of 10 g of the same sample?
Answer: Volume = 2 V; density = d

Question 3. The specific heat capacity of 10g of a sample of aluminum is x cal. g^-1 K^-1 . Is the value of the specific heat capacity of 5g of that sample\(\frac{x}{2}\) cal .g^-1 K^-1?
Answer:  No, because it is a state property of the system.

Read and Learn More NCERT Class 11 Chemistry Very Short Answer Questions

Question 4. On which factors does the change in a state function depend?
Answer: Upon initial and final states of the system.

Question 5. The initial state of a system is ‘This system participates in the following process: A→B→C→A. What will be the change in the internal energy of the system in this process?
Answer: Zero

Question 6. At T K, what will be the value of (H- U) for 1 mol of ideal gas?
Answer: RT

Question 7. In an isothermal expansion of an ideal gas, both ΔH and ΔU are zero. What will be the values of ΔU and ΔH in the isothermal compression of an ideal gas?
Answer: ΔH = 0; ΔU = 0

Question 8. What will be the value of the change in internal energy of a process occurring in an isolated system?
Answer: Zero

Question 9. In a process, q cal heat is absorbed by a closed system. If work done by the system is w cal, then what will be the value of the change in internal energy (ΔU) in this process?
Answer: ΔU = q-w,

Question 10. For a process occurring in a closed system, ΔU = q. If only pressure-volume work is performed by the system then which type of process is this?
Answer: Isochoric

Question 11. The amount of heat released by a system at constant pressure is 20 kj. What will be the value of ΔH in this process?
Answer: ΔH = -20 kj

Question 34. For an ideal gas C V,m = J mol^-1 K^-1. What will be the value of Cp m?
Answer: 20.784 J.mol^-1-K^-1?

Question 12. A liquid in a closed adiabatic container is stirred. Among ΔU, w, and q, which one will be zero?
Answer: q = 0

Question 13. If the temperature of I mol of an ideal gas is doubled then what will be the change in value of internal energy? Will it increase, decrease, or remain the same?
Answer: Will increase.

Question 14. 2H₂ + O₂-2H₂O , AH = -571.6 kj. Does this equation express the thermochemical equation for the formation of H₂O?
Answer: No, because the physical states of the reactants and products are not mentioned in the reaction.

Question 15. What temperature and pressure are usually considered as the standard state of a substance?
Answer: Pressure = 1 atm, any temperature may be considered.

Question 16. Which allotropic form of carbon is considered a source of carbon in the formation reactions of carbon compounds at 25°C and 1 atm?
Answer: C(graphite,s).

Question 17. Which of the following two reactions indicates the formation reaction of HI(g) at 25°C and 1 atm?

⇒ \(\frac{1}{2} \mathrm{H}_2(g)+\frac{1}{2} \mathrm{I}_2(g) \rightarrow \mathrm{HI}(g)\)

⇒ \(\frac{1}{2} \mathrm{H}_2(g)+\frac{1}{2} \mathrm{I}_2(s) \rightarrow \mathrm{HI}(g)\)

Answer: Reaction because the standard state of means than iodine is I2(s).

Question 18. Between O₂(g) and O₃(g), whose standard enthalpy of formation (ΔH0f) is taken as zero at 1 atm and 25°C?
Answer: O₂ (g) because at 25°C the standard state of oxygen is O₂(g)

Question 19. In which of the following reactions the standard heat of reaction is equal to the standard heat of formation of CaBr₂(s) at 25°C?

• Ca(s) + Br₂(l)-CaBr₂(s)
• Ca(s) + Br₂(g)-CaBr₂(s)

Answer: Reaction (1), because at 25X the standard state of bromine is Br2(l).

Question 20. Heat is required to vaporize 1 g of water at 100°C and 1 atm is 2.26kj. What is the enthalpy of vaporization of water at this temperature and pressure?
Answer: 40.68 kj

Question 21. 1 mol of H₂O(Z) is formed when 1 mol of H+ ions and 1 mol of OH- ions react together in aqueous solution. Does this reaction represent the formation reaction of water?
Answer: No, because H₂O(f) is not formed from its constituent elements.

Question 22. Consider the reactions

• A₂(s) + B₂(g)-+A₂(g) + B₂(g); AH = -x kj
• A₂(g) + B₂(g)-+2AB(g) ; AH = -y kj .

What is the value of the change in enthalpy for the following reaction A₂(s) + B₂(g)-+2AB(g)?
Answer: — (X + y) kJ ;

Question 23. S(monoclinic, s)-S(rhombic, s). What is the enthalpy change of this process called?
Answer: Heat of transformation

Question 24. \(\mathrm{H}_2(g)+\frac{1}{2} \mathrm{O}_2(g) \rightarrow \mathrm{H}^{+}(a q)+\mathrm{OH}^{-}(a q) ;\) \(\Delta H^0=-228.5 \mathrm{~kJ} \cdot \mathrm{mol}^{-1} \text { if } \Delta H_f^0\left[\mathrm{H}^{+}\right]=0\) then what will be the value of AH0Of[OH-] ?
Answer: -228.5 kj mol^-1

Question 25. The bond dissociation energies of three A-B bonds in ΔB3(g) molecule are x,y, and zkj-mol^-1 respectively. What is the bond energy of the A- B bond?
Answer: l/3(x + y + z)kJ-mol^-1

Question 26. Why is the heat of reaction of a reaction occurring in a bomb calorimeter equal to the change in internal energy of the reaction system?
Answer: The volume of the reaction system remains the same.

Question 27. In the case of diatomic gaseous I molecule 33. -7.43kJ -mol^-1 ;
Answer: In the case of diatomic gaseous molecules.

Question 28. What will be the difference between ΔH and ΔU in the combustion reaction of C₁₀H₈(g) at 25°C?
Answer: -7.43kJ -mol^-1

Question 29. Write down the relation between ΔH and ΔU for the following reaction: CH₃COOH(aq) + NaOH(a<y)-CH₃COONa(ag) + H2O(l)
Answer: zero

Question 30. If the bond energy of the C- H bond is +416.18 kj .mol^-1, then what will be the enthalpy of the formation of the C-H bond?
Answer: 416.18kJ. mol^-1

Question 31. What is the most important feature of Hess’s law?
Answer: It is used to determine the heat of the reaction;

Question 32. The standard bond dissociation energy of A2(g), B2(g) and AB(g) molecules are x,y, and zkj-mol-1 respectively. What will be the standard enthalpy of the formation of AB(g)?
Answer: [z- 1 /2(x + y)]kj . mol^-1

Question 33. At temperature T K the difference between ΔH and ΔU for the following reaction is \(+\frac{1}{2} R T: \mathrm{A}+\frac{1}{2} \mathrm{~B}_2(\mathrm{~g}) \rightarrow \mathrm{AB}(\mathrm{g}).\) What is the physical state of (solid or gas)?
Answer: Soild [A(s)]

Question 34. Give an example of a spontaneous process in which the change in enthalpy of the system is positive.
Answer: Melting of ice above 0°C,

Question 35. What will be the signs of enthalpy change and entropy change for a process to be spontaneous at all temperatures?
Answer: ΔH < 0 , ΔS > 0

Question 36. What will be the signs of AG for melting ice at 267K and 276K temperature and atm pressure?
Answer: ΔG> 0 ΔG < 0

Question 37. Water and ice remain in equilibrium at 0°C and 1 atm pressure. What will be the value of AG and the sign of the S system at this equilibrium?
Answer: ΔG = 0 , ΔS_sys>0,

Question 38. Which one of the following relation or expression is true for a spontaneous process of ΔG = 0, ΔH=TΔS, ΔG > 0, ΔG < 0?
Answer: AG<0

Question 39. What will be the sign of entropy change for the process I2(g)-+I2(s)?
Answer: ΔS = -ve

Question 40. What will be the change in entropy of the surroundings in a spontaneous process occurring in an isolated system?
Answer: Zero

Question 41. Is the entropy of the universe constant?
Answer: No, increases continuously

Question 42. Give an example of a process in which the change in enthalpy of the system is negative.
Answer: Solidification of liquid

Question 43. what sign (or-) of entropy change in an endothermic relation makes the reaction Non-spontaneous at any temperature?
Answer: ΔS < 0,

Question 44. In which case the Δ_sys will lie maximum between die following two processes ice – water I₂(s) – l₂(g)
Answer: I₂(s) – l₂(g)

Question 45. Predict the sign of AS0 for the given reaction. \(2 \mathrm{H}_2 \mathrm{~S}(g)+3 \mathrm{O}_2(g) \rightarrow 2 \mathrm{H}_2 \mathrm{O}(g)+2 \mathrm{SO}_2(g)\)
Answer: – ve

Question 46. Does die Gibbs free energy of a substance decrease or increase if the amount of the substance is increased?
Answer: Will increase

Question 7. In a process, the value of the change in entropy of the die system and its surroundings are x and -yj. IC^-1 . If x > y, then will the process be spontaneous?
Answer: No

Question 48. The change in entropy of the system in a process A -4 B -4 C is 25 J K^-1. If the change in entropy of the system in step B → C is 15 J K^-1, then what will be the change in entropy of the system in step B→ A?
Answer: -10J.K^-1

Question 49. Which is not a state function: (q+w), w, H, G?
Answer: ‘ w’ is not a state function it is not a property of the system.

Question 50. In a process, a system absorbs 500J of heat and performs 800J of work. In the process, q =__________ w =__________
Answer: As the system absorbs heat. and performs work, q is + ve and w is -ve. Hence, q = +500 J and w – -800 J.

Question 51. In a process, a system releases 500J of heat and work done on the system is 300 J. In the process, q = w =
Answer: The system releases heat and work is done on the system i.e., q is -ve and w is +ve so, q = -500J, w = +300J.

Question 52. Is rusting of iron a spontaneous process? What is the entropy of a system? Give its mathematical definition. What is its unit?
Answer: Rusting of irony is a spontaneous process.

Question 53. For a reversible process A = -20 J. K-1. What will be the value of ASsun in this process?
Answer: In a reversible process, ΔS_sys = (-) ΔS_surr As, Δ = -20 J⋅K-1.So, ΔS_surr = +20 J.K-1

Question 54. Write the SI unit of energy.
Answer: The SI unit of entropy is I K-

Question 55. A occurring in an isolated system does not have any effect on its surroundings and the process is ft influenced by its surroundings. Why?
Answer: An isolated system does not interact with its surroundings

Question 56. In a process, if the heat released by the system and 80 work done on the system are 90 ) and 120), respectively, then what will he of q and w?
Answer: q=-90J ad w=+120J.

Question 57. If the specific heat capacity and molecular mass of a gas are cp and M respectively then what will be the molar heat capacity of the gas?
Answer: Molar heat capacity of tyre gas, C_p,m = c_p x M.

Question 58. Give examples of two processes where AS is zero
Answer: Adiabatic reversible process Cyclic process

Question 59. What will be the change in entropy in an irreversible cyclic process?
Answer: As entropy is a state function, the change in entropy in either a reversible or an irreversible cyclic process is zero.

Question 60. Are the given statements correct? If bent Is absorbed In a chemical reaction, the reaction cannot be spontaneous. The entropy of the system may decrease In a reaction, but the reaction can occur spontaneously
Answer: The statement is incorrect is correct

Question 61. Which of the following conditions favours the spontaneity of a reaction at a constant temperature and pressure? ΔH > 0 , ΔH < 0 , ΔS > 0 , ΔS < 0
Answer: The conditions of ΔH < 0 and ΔS > 0 favour a reaction to be spontaneous at a constant temperature and pressure.

Question 62. For 311 isolated systems, ΔU = 0, what will be AS?
Answer: For a spontaneous process occurring in an isolated system AS is positive (i.e., ΔS > 0 ).

Question 63. Write the SI unit of entropy
Answer: SI unit of entropy: J. K-1. mol-1

Question 164. State the condition of spontaneity and equilibrium in terms of Gibbs free energy change of a system.
Answer: The condition of spontaneity regarding Gibbs free energy is AG < 0. The condition of equilibrium in terms of Gibbs free energy is AG = 0.

Question 165. Which variable is kept constant in an isochoric process?
Answer: Volume is kept constant in an isochoric process.

Question 166. In a process, 600J of heat is absorbed by a system, and 300J of work is done by the system. Calculate the change in internal energy of the system
Answer: Given: q = +600J, w = -300J. So, change in internal energy, ΔH = q + w = (600- 300)J = 300J

NCERT Solutions For Class 11 Chemistry Chapter 6 Chemical Thermodynamics Fill In The Blanks

Question 1. The sign of A U in the adiabatic expansion of a gas is ____________.
Answer: -ve

Question 2. In a process q > 0, but w = 0, So, the internal energy of the system will (Increase/decrease) ____________
Answer: Increase

Question 3. According to first Jaw, for a cyclic process q+w =____________
Answer: 0

Question 4. The volume of a substance is a property while the molar volume of a substance is an____________property.
Answer: Extensive, intensive

Question 5. The specific heat capacity of a substance is a; cal. g-1.°C^-1. The specific heat capacity of 100 g of that substance will be____________
Answer: x cal. g-1 °C^–1

Question 6. The molar heat capacity of a substance at constant pressure is ____________than that at constant volume.
Answer: Greater;

Question 7. In the vaporization of water, the signs of q and w are ____________and respectively.
Answer: q = + ve , w = -ve;

Question 8. For a process occurring at constant volume, U= + 10 kj. In this process, q = ____________
Answer: q = +10 kJ;

Question 9. In isothermal expansion of 1 mol of an ideal gas, q = + 12 kJ. The value of w = and A U =____________
Answer: w = -12 kJ , AU = 0

Question 10. In an alchemical reaction, if the total enthalpies of reactants and products are HR and Hp respectively then Hp > HR for____________ reaction and HR > Hp for ____________reaction.
Answer: Endothermic, exothermic

Question 11. At 25°C, the standard state of liquid ethanol means ____________ethanol at 25 °C and____________ pressure.
Answer: Pure liquid, 1 atm

Question 12. Given: C₃H₈(g) + 5O₂(g)→3CO₂(g) + 4H₂O(l) and C₃H₂(g) + 5O₂(S)→3CO₂(g) + 4H₂O(g). At a fixed temperature and pressure between these two reactions the heat evolved in the second reaction is more than that in the first one.
Answer: Less

Question 13. At 25°C and 1 atm, the standard reaction enthalpy for the reaction C(graphite, s) + O₂(g)→CO₂(g) is the ____________ of CO₂(g).
Answer: Standard enthalpy of formation;

Question 14. At 25°C and 1 atm, standard reaction enthalpy for the reaction, CH4(g) + 2O₂(g)→ CO₂(g) + 2H₂O(Z) is ____________of CH₄(g).
Answer: Standard enthalpy of combustion

Question 15. The change in enthalpy for die reaction HCN(aq) + NaOH(aq)—>NaCN(aq) + H₂O(Z) is ____________than the change ih! ^enthalpy for the reacdon HCI {aq) + NaOH(aq)→NaCl(aq) + H₂O(/).
Answer: Less

Question 16. The change in enthalpy for the process KCl(s) + 100H₂0(l)-KCl(100H₂O) is called____________.
Answer: Integral heat of solution

Question 17. At 25°C and 1 atm if the bond energy of Cl₂(g) is 242 kj.mol^-1, then the standard enthalpy of atomization of chlorine at the same temperature = ____________.
Answer: 121KJ.mol^-1

Question 18. In a reaction Δ_sys= xJ.K^-1 and ΔS_surr = -yJ.K^-1. The reaction will be spontaneous if ____________
Answer: x>y

Question 19. In the cyclic process ΔB Δ the changes in entropy of the system are ΔS₁, ΔS_2, and ΔS₃. ΔS₁ + ΔS₂ + ΔS₃ =____________.
Answer: Zero

Question 20. NH₄Cl(s) + H₂O(l) → NH₄⁺(aq) + Cl^–(aq). It is an endothermic process. In this process the signs (+ or -) of____________ ΔS_sys and ΔS_surr  are and respectively.
Answer: Δ_sys > 0 and ASsun < 0

Question 21. A reaction is non-spontaneous at all temperatures but the____________
reverse reaction is spontaneous at all temperatures. The signs (+ or – ) of ΔH and ΔS for the reverse reaction are____________and respectively.
Answer:  ΔH < 0 and Δ_sys

Question 22. In an exothermic process Δ_sys< 0. In this reaction the sys sign (+ or – ) of ASsurr is____________. This reaction will be spontaneous if the numerical value of Ssys is higher than that of ASsurr.
Answer: +ve, less

Question 23. In a spontaneous process occurring at constant pressure and at temperature T K, ΔH > 0, ΔS > 0. In this process, the numerical value of ΔH is ____________ than that of____________.
Answer: Less, TΔS

Question 24. A process is always spontaneous at all temperatures if the enthalpy change is and entropy changes is _______
Answer: —ve and +ve.