Which thermodynamic process is irreversible?
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Answer: C. Solution of NaCl in water at 50°C
Explanation
The spontaneous dissolution of sodium chloride in water is an irreversible thermodynamic process accompanied by mixing. Spontaneous mixing processes increase the total entropy of the isolated system and cannot reverse themselves. Overcoming lattice energy and dispersing hydrated ions generates dissipative changes that define irreversibility. Irreversible processes involve dissipative effects like friction, unrestrained expansion, or spontaneous chemical mixing. Reversible processes proceed infinitely slowly through a continuous sequence of equilibrium states without losses. Dissolving salt in water is a common thermodynamic example of a natural, spontaneous, one-way process.
Chemical engineers account for process irreversibility when calculating lost work and second-law efficiencies. Understanding spontaneity helps predict whether chemical solutions will form or remain separated over time. Industrial separation units require energy input to reverse spontaneous mixing and recover pure water or salt. Expansion of an ideal gas against constant pressure is also an irreversible thermodynamic process due to unrestrained flow. Vaporization of water at boiling point under constant pressure represents a reversible phase change condition. Stating none of these is wrong because spontaneous dissolution is definitively an irreversible process.
- Subject
- Engineering
- Category
- Chemical Engineering
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- —
- Difficulty
- medium
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