THERMODYNAMICS Quiz-1

 

CHEMISTRY THERMODYNAMICS QUIZ-1

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. Energy can transfer from system to surroundings as work if :

•  There is thermal equilibrium between system and surrounding
•  There is mechanical equilibrium between system and surrounding
•  If pressure of system > atmospheric pressure
•  None of these

Solution
W=P_exV

Q2.Temperature of 1 mol of a gas is increased by 1° at constant pressure. The work done is

•  R
•  2R
•  R/2
•  3R

Solution
W=P(∆V)
PV=RT
PV+∆V=R(T+1)
∴ P∆V=R

Q3.Carnot’s cycle is said to have 25% efficiency when it operates between T(source) and 300 K (sink). Temperature T is

•  300 K
•  350 K
•  375 K
•  400 K

Solution
η=(T2-T1)/T2; T1=temperature of sink
T2=temperature of the source
0.25=(T2-T1)/T2

Q4.Since the enthalpy of elements in their natural state is taken to be zero, the heat of formation (∆_fH) of compounds

•  Is always negative
•  Is always positive
•  May be negative or positive
•  Is zero

Solution
May be negative or positive

Q5.The dissolution of NH₄Cl in water is endothermic even through NH₄Cl dissolves in water spontaneously. Which one of the following best explains this behaviour?

•  The bonds on solid NH₄Cl are weak
•  The entropy-driving force causes dissolution
•  Endothermic processes are energetically favourable
•  The dissolving process is unrelated to energy

Solution
 The entropy-driving force causes dissolution

Q6.Under which of the following condition is the relation ∆H=∆U+P∆V valid for a closed system at

•  Constant pressure
•  Constant temperature
• Constant temperature and pressure
•  Constant temperature, pressure and composition

Solution
Constant temperature

Q7.When a reaction is carried out in a closed vessel

•  q_P < q_V
•  q_P > q_V
•  q_P = q_V
•  q_{V = 0}

Solution
q_P = q_V

Q8.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
C₂H₅SH+9/2O₂(g)⟶2CO₂(g)+3H₂O(l)+SO₂(g)

Q9.For an endothermic reaction where ∆H represents the enthalpy of the reaction in kJ mol^-1, the minimum value for the energy of activation will be

•  Less than ∆H
•  Zero
•  More than ∆H
•  Equal to ∆H

Solution
Equal to ∆H

Q10. For the gaseous reaction involving the complete combustion of isobutene

•  ∆H = ∆U
•  ∆H > ∆U
•  ∆H = ∆U = 0
•  ∆H < ∆U

Solution
∆H > ∆U
C₄H₁₀+O₂⟶CO₂+H₂O