THERMODYNAMICS Quiz-2

 

CHEMISTRY THERMODYNAMICS QUIZ-2

Dear Readers,

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. If S+O₂→SO₂; ∆H=-298.2 kJ
SO₂+12O₂→SO₃; ∆H=-98.7 kJ
SO₃+H₂O→H₂SO₄; ∆H=-130.2 kJ
H₂+12O₂H₂O; ∆H=-287.3 kJ
Then the enthalpy of formation of H₂SO₄ at 298 K is:

•  -814.4 kJ
•  -650.3 kJ
•  -320.5 kJ
•  -233.5 kJ

Solution
-650.3 kJ

Q2.The products of combustion of an aliphatic thiol (RSH) at 298 K are

•  CO₂(g), H₂O(g), and SO₂(g)
•  CO₂(g), H₂O(l), and SO₂(g)
•  CO₂(l), H₂O(l), and SO₂(g)
•  CO₂(g), H₂O(l), and SO₂(l)

Solution
CO₂(g), H₂O(l), and SO₂(g)

Q3.For hypothetical reversible reaction
1/2A₂(g)+3/2B₂(g)→AB₃(g); ∆H=-20kJ if standard entropies of A₂,B₂and AB₃ are 60, 40, and 50 J K^-1mol^-1, respectively. The above reaction will be equilibrium at

•  400 K
•  500 K
•  250 K
•  200 K

Solution
At equilibrium, ∆S_Total = 0
∴ S_P^⊖-S_R^⊖ = 0

Q4.C_P-C_V=R. This R is

•  Change in KE
•  Change in rotational energy
•  Work done which system can do on expanding the gas per mol per degree increase in temperature
•  All correct

Solution
PV = RT at temperature T for one mole
PV+∆V=R(T+1) at temperature (T+1) for one mole
∴ P∆V = R

Q5.For which of the following equations, will ∆H be equal to ∆U?

•  H₂(g)+1/2O₂(g)→H₂O(l)
•  H₂(g)+I₂(g)→2HI(g)
•  2NO₂(g)→N₂O₄(g)
•  4NO₂(g)+O₂(g)→2N₂O₅(g)

Solution
 ∆H = ∆U+∆nRT
In (b), ∆n=0
∴ ∆H = ∆U

Q6.A reaction, A+B⟶C+D+q, is found to have a positive entropy change, the reaction will be:

•  Possible at high temperature
•  Possible only at low temperature
• Not possible at any temperature
•  Possible at any temperature

Solution
Possible at any temperature

Q7.For the combustion reaction at 298 K
2Ag(s)+1/2O₂(g)→2Ag₂O(s)
Which of the following alternatives is correct?

•  ∆H = ∆U
•  ∆H > ∆U
•  ∆H < ∆U
•  ∆H and ∆U bear no relation with each other

Solution
∆H = ∆U+∆nRT
∆n = n_P-n_R
∴ ∆n = (2) - (5/2) = (-1/2)
∴ ∆H = ∆U - (1/2)RT
∴ ∆U = ∆H + (1/2)RT
Or ∴ ∆U > ∆H

Q8.Enthalpy of the system is given as

•  H + PV
•  U + PV
•  U - PV
•  H - PV

Solution
H = U + PV

Q9.In thermodynamics, a process is called reversible when

•  The surroundings and system change into each other
•  There is no boundary between the system and surroundings
•  The surroundings are always in equilibrium with the system
•  The system changes into the surroundings spontaneously

Solution
The surroundings are always in equilibrium with the system

Q10. For the reversible process, the value of ∆S is given by the expression

•  ∆H/∆T
•  T/q(rev)
•  q(rev)×T
•  q(rev)/T

Solution
∆S=q_rev/T