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“Thermodynamics” is a branch of science that pacts with the connection between heat and other aspects of energy. A portion of the universe where observations are made is called a system. The surrounding of a system is the portion of the universe that does not encompass the system.
Based on the swap of energy and matter, thermodynamic systems can be categorized into 3 types: closed system, open system, and isolated system. In a closed system, only energy can be swapped with the surrounding. In an open system, energy, as well as matter, can be swapped with the surrounding. In an isolated system, both energy and matter cannot be swapped with the surrounding.
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Thermodynamics MCQs
Ques. Which law of thermodynamics provides a method to evaluate which property?
- Absolut Energy
- Absolute Enthalpy
- Absolute Entropy
- Absolute Free EAll-natural
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Ans. (C) Absolute entropy
Explanation: The Third Law of Thermodynamics is interned with the limiting behavior of systems as the temperature reaches absolute zero. Greatly Thermodynamics Estimations use only entropy variations, so the zero point entirely in scale is often not significant. However, the Third Law tells us about the exact as it describes the condition of zero entropy.
Ques. One mole of which of the following has the biggest entropy?
- Liquid Nitrogen
- Hydrogen Gas
- Mercury
- Diamond
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Ans. (b) Hydrogen Gas
Explanation: The measure of randomness of an entity is called entropy. The randomness of molecules of a substance is tremendous is the entropy. Here hydrogen gas has extra entropy as it exhibits more randomness/disorderliness due to less molar mass than all the provided substances and also in the gas stage.
Ques. The variation which by definition has ZERO standard molar enthalpy of formation at 298 K is
- Br2(g)
- Cl2(g)
- H2O(g)
- CH4(g)
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Ans. (b) Cl2(g)
Explanation: This is feasible only for elements, chlorine is a gas at this temperature, but bromine is a liquid, so it is feasible only for chlorine.
Read more : Phase Transition
Ques. In which of the following processes, an ultimate increase in entropy is examined?
- Dissolution of Salt in Water
- Condensation of Water
- Sublimation of Naphthalene
- Melting of Ice
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Ans. (c) Sublimation of Naphthalene
Explanation: The rule of entropy in solid, liquid and gas is gas > liquid > solid .Hence, in the sublimation of naphthalene, a maximum proliferation in entropy is examined.
Ques. Which thermodynamic function catalogs automatically for enthalpy and entropy both?
- Helz Free Energy
- Internal Energy
- Work Function
- Gibbs Free Energy
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Ans. (d) Gibs Free Energy
Explanation: Gibbs’s free energy incorporates the impact of both enthalpy and entropy. The change in free energy (ΔG) is proportional to the sum of the change of enthalpy (?H) minus the product of the temperature and the change of entropy (?S) of the system.
?G = ?H – T?S
ΔG indicates the direction in which a chemical reaction will go under two conditions: (1) constant temperature and (2) constant pressure.
If ΔG is positive, then the reaction is not spontaneous (it expects the intake of external energy to occur) and if it is negative, then it is spontaneous (arises without the intake of any external energy).
Ques. The temperature of the system reduces in an ______.
- Adiabatic Compression
- Isothermal Expansion
- Isothermal Compression
- Adiabatic Expansion
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Ans. (d) Adiabatic Expansion
Explanation: In the adiabatic process, heat is neither expanded nor eliminated from the stem. So the work done by the system (expansion) in the adiabatic process will result in a decrease in the internal energy of that system (from the first law).
As internal energy is directly proportional to the change in temperature there will be a temperature drop in an adiabatic process.
Read More: Atomic Mass of Elements Important Notes
Ques. Heat cannot by itself flow from a body at a lower temperature to a body at a higher temperature is a statement as a consequence of
- Conservation of mass
- Conservation of momentum
- First law of thermodynamics
- Second law of thermodynamics
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Ans. (d) Second law of thermodynamics
Explanation: As energy is transmitted or changed, more and more of it is lost, according to the second law of thermodynamics. It's one of the four principles of thermodynamics, which explain how thermal energy, or heat, interacts with other types of energy and how energy affects matter.
Ques. The enthalpy change in a reaction does not hinge upon
- The state of reactions and products
- The nature of the reactants and products
- Different intermediate steps in the reaction
- Initial and final enthalpy of the reaction
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Ans. (c) Different intermediate steps in the reaction
Explanation: The enthalpy change is a state function so it doesn’t depend on various moderate steps in the reaction.
Ques. When water is expanded to quick lime the reaction is
- Explosive
- endothermic
- exothermic
- photochemical
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Ans. (c) exothermic
Explanation: When water is expanded to quick lime the reaction is exothermic
CaO + H2O → Ca(OH)2 ?H =:ve
Ques. Closed system consists of which type?
- first
- second
- third
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Ans. (a) first
Explanation: In a closed system, only energy can be swapped with the surrounding.
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