## CHEMICAL THERMODYNAMICS QUIZ-7

The one subject in NEET which is candidates who can easily attain good marks is Chemistry. That's the reason, often, one doesn’t pay notice and choose to compromise it. But if one wants to rank above others, the tip is to be thorough with NEET chemistry concepts. The understanding of reactions and definite basic understanding is what requires major attention in Chemistry but once done it only gets simpler from there. The main focus on the to-do list should be on getting a hang of the NCERT syllabus of NEET chemistry..

Q1. Given, C+O2→CO2+94.2 kcal ….(i)
H2+1/2 O2→H2O+68.3 kcal ….(ii)
CH4+2O2→CO2+2H2O+210.8 kcal ….(iii)
The heat of formation in kcal will be :
•  45.9
•  47.8
•  - 20.0
•  47.3
Solution
(c) C+2H2→CH4; ∆H= ?
Find ∆H by eqs. (i) + 2 × (ii) – (iii)
Q2.Which of the following expressions represents the first law of thermodynamics?
•  ∆E=-q + W
•  ∆E=q - W
•  ∆E=q + W
•  ∆E=-q - W
Solution
c)
Q3.  The first law of thermodynamic is expressed as
•  q - W=∆E
•  ∆E=q - W
•  q=∆E - W
•  W=q + ∆E
Solution
(c) The first law of thermodynamics can be expressed as :
∆E=q+W
q=∆E-W

Q4. A heat engine absorbs heat Q1 at temperature T1 and heat Q2 at temperature T2 work
done by the engine is (Q1+Q2) this data
•  Violates 1st law of thermodynamics
•  Violates 1st law of thermodynamics if a1 is –ve
•  Violates 1st law of thermodynamics if a2 is -ve
•  Does not violates 1st law of thermodynamics
Solution
(d) It does not violate the first law of thermodynamics but violates the II law of thermodynamics
Q5.Mark the correct statement
•  For a chemical reaction to be feasible, ∆G should be zero
•  Entropy is a measure of order in a system
•  For a chemical reaction to be feasible, ∆G should be positive
•  The total energy of an isolated system is constant
Solution
(d)
Q6. The correct thermochemical equation is :
•  C+O2⟶CO2; ∆H= -94 kcal
•  C+O2 ⟶ CO2; ∆H= +94 kcal
•  C(s)+O2(g) ⟶ CO2(g); ∆H= -94 kcal
•  C(s)+O2 (g)⟶CO2(g); ∆H= +94 kcal
Solution
(c) It provides information about physical states of reactants and products as well as about thermal changes. (d) is wrong because combustion is exothermic.
Q7.Entropy change of fusion at constant pressure is given by:
•  ∆S(f)=∆Hf/T
•  ∆S(f)=∆Gf/T
•  ∆S(f)=(∆Hf)/∆T
•  None of these
Solution
(a) This is derived formula.
Q8.Gibbs energy G, enthalpy H and entropy S are related by:
•  G=H + TS
•  G=H - TS
•  G - TS=H
•  S=H - G
Solution
(b) Gibbs energy change ∆G is given by:
∆G=∆H-T∆G
Also, G=H-TS
Q9. If, combustion of 4 g of CH4 liberates 2.5 kcal of heat, the heat of combustion of CH4 is :
•  -2 kcal mol-
•  -10 kcal mol-
•  2.5 kcal mol-1
•  -5 kcal mol-1
Solution
(b) ∆H=(2.5 ×16)/4= -10 kcl mol-1
Q10. The ∆Hfo of O3,CO2,NH3 and HI are 142.2 -393.3,-46.2 and +25.9 kJ per mol respectively.
The order of their increasing stabilities will be
•  O3,CO2,NH3,HI
•  CO2,NH3,HI,O3
•  O3,HI,NH3,CO2
•  NH3,HI,CO2,O3
Solution
(c) Energy absorbed ∝1/(stability of compound)
Energy released ∝ stability of compound
Thus, the order of stability is
142.2>25.9>-46.2>-393.2
ie,O3>HI>NH3>CO2 ## Want to know more

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Chemical Thermodynamics Quiz-7
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