THERMODYNAMICS Quiz-7

CHEMISTRY THERMODYNAMICS QUIZ-7

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IIT JEE exam which consists of JEE Main and JEE Advanced is one of the most important entrance exams for engineering aspirants. The exam is held for candidates who are aspiring to pursue a career in the field of engineering and technical studies.
Chemistry is important because everything you do is chemistry! Even your body is made of chemicals. Chemical reactions occur when you breathe, eat, or just sit there reading. All matter is made of chemicals, so the importance of chemistry is that it's the study of everything..

Q1.In which of the following process ∆H and ∆U are of same magnitude:

•  Evaporation of CCl₄(l)
•  CaCO₃(s) ⟶ CaO(s) + CO₂(g)
•  NH₄Cl(s) ⟶ NH₄Cl(g)
•  2HI(g) ⟶ H₂(g) + I₂(g)

Solution
∆H = ∆U + ∆nRT
∆n = 0 = n_P - n_R
∴ ∆H = ∆U

Q2.1 g H₂ gas STP is expanded so that the volume is doubled. Hence, work done is

•  22.4 L-atm
•  5.6 L-atm
•  11.2 L-atm
•  44.8 L-atm

Solution
V1 (volume of 1 g H₂) = 11.2 L at STP
V2 (volume of 1 g H₂) = 22.4 L
∴ W = P∆V = 11.2 L atm

Q3.For the equations
C(diamond) + 2H₂(g) → CH₄(g) ∆H1
C(g) + 4H(g) → CH₄(g) ∆H2
Predict whether

•  ∆H1 = ∆H2
•  ∆H1 > ∆H2
•  ∆H1 < ∆H2
•  ∆H1 = ∆H2 + ∆_vapH(C) + ∆_dissH(H₂)

Solution
∆H1 > ∆H2

Q4.For the reaction
X₂O₄(l) → 2XO₂(g)
∆U = 2.1 kcal, ∆S = 20 cal K^-1 at 300 K
Hence, ∆G is

•  2.7 kcal
•  -2.7 kcal
•  9.3 kcal
•  -9.3 kcal

Solution
∆H = ∆U + ∆n_gRT
= 2.1×2×0.002×300 = 3.3 kcal
∆G = ∆H - T∆S
= 3.3×-300×0.02 = -2.7 kcal

Q5.

•  ∆H/nF
•  ∆G/nF
•  ∆S/nF
•  -∆S/nF

Solution
 

Q6.For an ideal gas Joule-Thomson coefficient is

•  Positive
•  Negative
• Zero
•  Dependent on molecular weight

Solution
In an ideal gas, there is no force of attraction between molecules.
Hence, no heat is lost in the expansion

Q7.Which of the following type of energies are involved in Born Haber’s cycle?

•  ∆_subH
•  Ionization energy
•  Bond dissociation energy
•  Lattice energy

Solution
(a,b,c,d)
Born-Haber cycle

Q8.The correct expressions for an adiabatic process are

•  T2/T1 = (V1/V2)^γ-1
•  P2/P1 = (T1/T2)^γ-1/γ
•  P₁V₁^γ = P₂V₂^γ
•  P₁V₁^γ-1 = P₂V₂^γ-1

Solution
(a,c)

Q9.The heat of combustion of enthanol was determined in a bomb calorimeter and was found to be -670.48 kcal mol^-1 at 25°C. What will be ∆U for the same reaction at 298K?

•  - 335.24 kcal
•  - 669.28 kcal
•   -670.48 kcal
•   +670.48 kcal

Solution
- 335.24 kcal

Q10. In which of the following cases entropy increases?

•  Solid changing to liquid
•  Expansion of a gas
•  Crystals dissolve
•  Boiling of an egg

Solution
(a,b,c)