- Heat does not spontaneously flow from a colder body to a hotter one. Which of the following thermodynamics law states this?
(a) Zeroth law of thermodynamics
(b) First law of thermodynamics
(c) Second law of thermodynamics
(d) Third law of thermodynamics
Answer: (c)
Video Explanation - Which of the following is an application of thermodynamics?
(a) Refrigerators
(b) Gas compressors
(c) Power plants
(d) All of the mentioned
Answer: (d)
Explanation
The second law of thermodynamics applies to all refrigerators, deep freezers, industrial refrigeration systems, all forms of air-conditioning systems, heat pumps, and so on. Thermodynamic cycles govern the operation of all forms of air and gas compressors, blowers, and fans. The study of the feasibility of employing various forms of renewable energy sources for household and commercial purposes is an important topic area of thermodynamics.
Video Explanation - Which of the following is a type of thermodynamic system?
(a) Open system
(b) Closed system
(c) Thermally isolated system
(d) All of the mentioned
Answer: (d)
Explanation
The types of thermodynamic systems are:
i) Open system
ii) Closed system
iii) Thermally isolated system
iv) Mechanically isolated system
v) Isolated system
Video Explanation - Which of the following occurs without a change in the internal energy?
(a) Isochoric process
(b) Isenthalpic process
(c) Steady-state process
(d) Isenthalpic process
Answer: (c)
Explanation
The following are some of the most commonly studied thermodynamic processes:
i) Heat does not lose or acquire energy in an adiabatic process.
ii) At a constant enthalpy, the isenthalpic process occurs.
iii) The isobaric process happens when the pressure remains constant.
iv) The isochoric process (also known as isometric/isovolumetric) happens at a constant volume.
v) At a constant temperature, an isothermal process occurs.
vi) Internal energy does not change in a steady-state operation.
vii) Isentropic process: adiabatic reversible process with constant entropy.
Video Explanation - What is the value of the absolute thermodynamic temperature scale?
(a) 3K
(b) 0K
(c) 1K
(d) 4K
Answer: (b)
Explanation
The temperature of an object on a scale with 0 as absolute zero is known as absolute temperature, also known as thermodynamic temperature.
Kelvin and Rankine are absolute temperature scales.
Video Explanation
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- Which of the following follows the Carnot theorem?
(a) Heat engines
(b) Gas turbine engines
(c) Gas compressors
(d) All of the mentioned
Answer: (d)
Explanation
Carnot’s Theorem
Carnot’s theorem, also known as Carnot’s rule, or the Carnot principle, can be stated as follows:
No heat engine operating between two heat reservoirs can be more efficient than a reversible heat engine operating between the same two reservoirs.
The simplest way to prove this theorem is to consider the scenario shown below, in which we have an irreversible engine as well as a reversible engine operating between the reservoirs TH and TL, however the irreversible heat engine has a higher efficiency than the reversible one.
Video Explanation
7.Which of the following processes is used to do maximum work done on the ideal gas that is compressed to half of its initial volume?
(a) isothermal
(b) isochoric
(c) isobaric
(d)adiabatic
Answer: (d)
Video Explanation
- What is the ratio of Cp/Cv for gas if the pressure of the gas is proportional to the cube of its temperature and the process is an adiabatic process?
(a) 2
(b) 3/2
(c) 4/3
(d) 5/3
Answer: (b)
Video Explanation - Which of the following laws was formulated by Nernst?
(a) First law of thermodynamics
(b) Second law of thermodynamics
(c) Third law of thermodynamics
(d) None of the above
Answer: (c)
Video Explanation - The standard condition for enthalpy changes are
(a) the pressure of 100 kPa
(b) temperature 298K
(c) normal physical state
(d) all of above
Answer: (d)
Explanation
If we are to compare the enthalpy changes of a various reactions we must use standard conditions, such as known temperature, pressures, amounts and concentrations of reactants or products.
The standard conditions are: A pressure of 1atm, a temperature of 298K. The standard conditions in most cases are known as STP.
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- The application of law of thermodynamics to the enthalpy change was done by
(a) Newton
(b) Hess’s
(c) Lewis
(d) Sophocles
Answer: (b)
Video Explanation - Pick out the Clausius-Clapeyron equation from the following?
(a) dP/dT = ΔH/TΔV
(b) ln P = – (ΔH/RT) + constant
(c) ΔF = ΔH + T [∂(ΔF)/∂T]P
(d) None of these
Answer: (b)
Video Explanation - Clausius Clapeyron equation applies to the _ process?
(a) Sublimation
(b) Melting
(c) Vaporisation
(d) All A., B. & C.
Answer: (d)
Video Explanation - Which of the following requirement is satisfied by a phase change of the first order?
(a) there are changes of volume and entropy
(b) the first-order derivative of the Gibbs function changes discontinuously
(c) both of the mentioned
(d) none of the mentioned
Answer: (c)
Explanation
We describe a first-order phase transition of a simple system in a process where the volume is kept constant. We show that, unlike what happens when the pressure is constant,
(i) the transformation extends over a finite temperature (and pressure) range,
(ii) each and every extensive potential (internal energy U, enthalpy H, Helmholtz energy F, and Gibbs energy G), and the entropy S is continuous across the transition, and
(iii) the constant-volume heat capacity does not diverge during the transition and only exhibits discrete jumps.
Video Explanation
15.What is the mathematical formula for Boyle-Van’t Hoff law ?
(a) p ∝ C
(b) p ∝ nV
(c) p ∝ 1V
(d) π ∝ nV
Answer: (d)
Explanation
The van’t Hoff-Boyle’s law states that at constant temperature the volume of an ideal gas is inversely proportional to the pressure of the gas.
Van’t Hoff Boyle Law of solution :
→ At constant temperature the osmotic pressure (⊓) of a delute solution is directly proportional to its molar concentration (C) or inversely proportional to volume (V) of the solution.
Explanation : π∝C but C=Vn
∴π∝Vn→π∝V1
Or say πV= constant [ n is no. of moles of solute dissolved in liters ]
Van’t Hoff Charle’s Law of solution :
→The concentration remaining constant, the osmotic pressure (π) of a dilute solution is directly proportional to absolute temperature (T) of the solution.
Explanation : π∝T
Tπ= constant.
Video Explanation
- Which is true for the entropy of a spontaneous reaction? (PPSC 2021)?
(a) ΔS(system) – ΔS(surroundings) > 0
(b) ΔS(system) + ΔS(surroundings) > 0
(c) ΔS(surroundings) > 0 only
(d) ΔS(system) > 0 only
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