Question

Which of the following properties will change when system containing solution 1 will become solution 2 ? 

• A. Molar heat capacity
• B. Density
• C. Concentration
• D. Gibbs free energy

Hint:

Distinguish between intensive and extensive properties. Intensive properties do not depend on the amount of substance, while extensive properties do.

Answer 1

The Correct Option is D

To determine which property will change when the system transitions from Solution 1 to Solution 2, let’s analyze each option based on the changes depicted in the diagram.

1. Molar Heat Capacity: This property is defined per mole of the substance and is not directly dependent on concentration changes. Therefore, changing from Solution 1 to Solution 2 doesn’t inherently alter molar heat capacity.
2. Density: Density is a function of mass per unit volume. Since adding more solute changes both the mass and volume proportionally, the overall density may not necessarily change by the transition alone.
3. Concentration: Concentration, defined as the amount of solute per unit volume of solution, is affected by this process. However, it isn't the primary focus in the context of the options provided.
4. Gibbs Free Energy (\(G\)): Gibbs free energy is a thermodynamic property that can change with the state of the system. When converting one solution to another by adding solute or solvent, Gibbs free energy changes due to changes in concentration and, consequently, chemical potential.
   • The change in Gibbs free energy (\( \Delta G \)) is often related to the work that can be done by the system before reaching equilibrium.
   • Since the concentration change affects the potential for extra work, the correct change when moving from Solution 1 to Solution 2 is in the Gibbs free energy.

Therefore, the correct answer is Gibbs free energy, as the change from Solution 1 to Solution 2 impacts the system’s thermodynamic properties.

Answer 2

Sol. Both solutions are having same composition, which is 1 mole of 'x' in 1L \( H_2O \), so all the intensive properties will remain same, but as total amount is greater in solution '1' compared to solution '2'. 
So extensive properties will be different hence Gibbs free energy will be different.