Thermodynamics Quiz-13

Thermodynamics is a very important branch of both chemistry and physics. It deals with the study of energy, the conversion of energy between different forms and the ability of energy to do work. Thermodynamics is an important chapter for JEE Mains, JEE Advance NEET and many others exams. As this chapter is present in both chemistry and physics and there is only a minor difference between them hence it becomes more important topic. It is not a tough topic, it only requires practice. This topic has been given good weightage in all engineering exams. So don't skip this and prepare well. All the best !.

Q1. The amount of heat measured for a reaction in a bomb calorimeter is
•  Î”G
•  Î”H
•  Î”E
•  pÎ”V
Solution:-
Bomb calorimeter measures qv, which is equal to Î”E.

Q2. The standard heat of formation of NO2(g) and N2O4(g) are 8.0 and 2.0 kcal/mol respectively. The heat of dimerization of NO2 in kcal is:
•  10.0
•  −6.0
•  −12.0
•  −14.0
Solution:-

Q3. Which reaction is endothermic in nature ?
•  CaCO3 → CaO + CO2
•  C + O2 → CO2
•  NaOH + HCl → NaCl + H2O
•  CH4 + 2O2 → CO2 + 2H2O
Solution:-
Decomposition of CaCO3 is made on heating.

Q4. The work done in an open vessel at 300 K, when 112g iron reacts with dil. HCl is :
•  102 kcal
•  0.6 kcal
•  0.3 kcal
•  0.2 kcal
Solution:-

Q5. Joule-Thomson expansion is
•  Isobaric
•  Isoenthalpic
•  Isothermal
•  None of these
Solution:-
Isoenthalpic

Q6. Heat of formation of H2O(g) at 1 atm and 25°C is −243 kJ. Î”U for the reaction,
H2(g) + 1/2 O2(g) → H2O(g) at 25°C is :
•  241.8 kJ
•  −241.8 kJ
•  −243 kJ
•  243 kJ
Solution:-
Î”H = Î”U + Î”nRT
Î”n = − 1/2
∴   −43 = Î”U + (−1/2) × 8.314 × 298 × 10−3
∴ Î”U = −241.76 kJ

Q7. Diborane is a potential rocket fuel which undergoes combustion according to equation :
B2H6(g) + 3O2(g) → B2O3(g) + 3H2O(g)
Calculate the enthalpy change for the combustion of diborane. Given :
•  +2035 kJ/mol
•  −2035 kJ/mol
•  +2167 kJ/mol
•  −2167 kJ/mol
Solution:-
For the equation
B2H6(g) + 3O2(g) → B2O3(g) + 3H2O
eq.(i) + 3(ii) + 3(iii) − (iv)
Î”H = −1273 + 3(−286) + 3(44) − 36
= −2035 kJ/mol

Q8. In a closed insulated container a liquid is stirred with a paddle to increase the temperature, which of the following is true ?
•  Î”U + W ≠ 0 , q = 0
•  Î”U = W = q ≠ 0
•  Î”U = 0, W = q ≠ 0
•  W = 0, Î”U = q ≠ 0
Solution:-
For insulated container, q = 0.

Q9. C(s) + O2(g) → CO2(g),   Î”H = −393.5 kJ and
CO(g) + 1/2 O2(g) → CO2(g),   Î”H = −283.5 kJ
then the heat of formation of CO is :
•  −110.0 kJ
•  +676.5 kJ
•  −676.5 kJ
•  +110.0 kJ
Solution:-
C(s) + O2(g) → CO2(g);     Î”H = −393.5 kJ
CO(g) + 1/2 O2(g) → CO2(g);     Î”H = −283.5 kJ
On subtracting,   C(s) + 1/2 O2(g) → CO(g);     Î”H = −110.0 kJ

Q10. Equal volume of 1M HCl and 1M H2SO4 are neutralised by dil. NaOH solution and x and y kcal of heat are liberated respectively. Which of the following is true ?
•  x = y
•  x = 0.5y
•  x = 0.4y
•  None of these
Solution:-
1M H2SO4 = 2 eq. H2SO4
1M HCl = 1 eq. HCl
Thus, for equal volume of two acids to be neutralized separately with NaOH, heat evolved will be twice in case of H2SO4 to that of HCl.

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