Chemical Thermodynamics Quiz - ICSE Class 11 Chemistry
Free practice quiz: Chemical Thermodynamics (ICSE Class 11 Chemistry). 45 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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For a process to be spontaneous at constant temperature and pressure, the correct thermodynamic condition is:
- ΔG > 0
- ΔG < 0
- ΔG = 0
- ΔH < 0
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Answer: B. ΔG < 0
Gibbs Free Energy (ΔG) is the criterion for spontaneity at constant temperature and pressure. A process is spontaneous if ΔG is negative (ΔG < 0), non-spontaneous if ΔG is positive (ΔG > 0), and at equilibrium if ΔG is zero (ΔG = 0).
Which statement best describes the second law of thermodynamics?
- Energy can be created or destroyed.
- The entropy of an isolated system never decreases.
- The total energy of an isolated system is constant.
- The entropy of the universe is always negative.
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Answer: B. The entropy of an isolated system never decreases.
The second law of thermodynamics states that the total entropy of an isolated system can only increase over time, or remain constant in ideal cases where the system is in a steady state or undergoing a reversible process. It essentially means that natural processes tend to move towards greater disorder.
A process is endothermic and spontaneous at all temperatures. What can be said about ΔH and ΔS?
- ΔH > 0, ΔS > 0
- ΔH < 0, ΔS < 0
- ΔH > 0, ΔS < 0
- ΔH < 0, ΔS > 0
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Answer: A. ΔH > 0, ΔS > 0
For a process to be spontaneous, ΔG < 0. The equation is ΔG = ΔH - TΔS. If the process is endothermic, ΔH > 0. For it to be spontaneous at all temperatures, the -TΔS term must be sufficiently negative to overcome the positive ΔH. This means ΔS must be positive (ΔS > 0).
The conversion of diamond to graphite at 298 K is an endothermic process (ΔH > 0). However, it is spontaneous. Which of the following must be true?
- ΔS > 0
- ΔS < 0
- ΔG < 0
- TΔS > ΔH
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Answer: D. TΔS > ΔH
For a spontaneous process, ΔG < 0. The Gibbs free energy equation is ΔG = ΔH - TΔS. Since ΔH is positive, for ΔG to be negative, the term -TΔS must be more negative than ΔH is positive. This implies that TΔS must be positive and greater than ΔH.
Which of the following thermodynamic cycles involves the isothermal compression of a gas, adiabatic expansion of the gas, isothermal expansion of the gas, and adiabatic compression of the gas?
- Carnot cycle
- Rankine cycle
- Otto cycle
- Diesel cycle
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Answer: A. Carnot cycle
The Carnot cycle is a theoretical thermodynamic cycle that describes the most efficient possible heat engine operating between two temperature reservoirs. It consists of four reversible processes: two isothermal processes and two adiabatic processes.