For which of the following processes would the entropy change be positive?
Choose one answer.
a. Hg(l)(45C)----- Hg(l)(25C)
b. H2O(l----H2O(s)
c. He (g) (1 atm)------- He(g)(10 atm)
d. I2(s)------I2(aq)
e. Ag+ (aq) +Br-(aq)------AgBr(s)
I figure that it wasn't A or B but the others not quite certain after reading my Chem book.
I don't understand the a answer so I can't comment.
You;re right about b.
I think c is wrong; entropy should increase the other way.
You know e can't be right; free-wheeling ions in solution to a crystal lattice is negative S.
But for d, if we go from a lattice structure in the solid to a liquid system, the entropy will increase.
It is indeed D.
Think about it this way:
I2(solid) turns into I2(aqueous). This means that, in basic terms, it is melting. Entropy increases when substances melt, vaporize, or sublime.
To determine which of the given processes will have a positive entropy change, we need to consider the factors that affect entropy.
Entropy is a measure of the randomness or disorder in a system. The general rule of thumb is that processes that increase the randomness or disorder of a system will have a positive entropy change.
Let's go through each option and analyze the changes in randomness for each process:
a. Hg(l)(45C) ----- Hg(l)(25C)
In this process, the substance remains in the liquid phase, and there is no change in the randomness or disorder of the system. Therefore, the entropy change for this process is likely to be zero or close to zero. So, option a is not likely to have a positive entropy change.
b. H2O(l) ---- H2O(s)
When water freezes, it undergoes a phase change from a liquid to a solid. In this process, the randomness or disorder decreases because the water molecules in the liquid state are more chaotic and randomly distributed compared to the solid state, where they form a structured lattice. Therefore, the entropy change for this process is negative, not positive.
c. He(g)(1 atm) ----- He(g)(10 atm)
Increasing the pressure of a gaseous substance leads to a decrease in volume and a decrease in randomness. Therefore, the entropy change for this process is negative, not positive.
d. I2(s) ----- I2(aq)
The process involves dissolving a solid solute (I2) in a solvent (water) to form a solution. Dissolution generally increases the randomness or disorder in a system. When the solid iodine is dissolved in water, the iodine molecules disperse into the solution, resulting in an increase in randomness. Therefore, the entropy change for this process is likely to be positive.
e. Ag+(aq) + Br-(aq) ----- AgBr(s)
This process involves the formation of a solid precipitate (AgBr) from the aqueous solutions of Ag+ and Br-. The formation of a solid from aqueous ions decreases the randomness or disorder in the system, as the otherwise freely moving ions become locked in a solid structure. Therefore, the entropy change for this process is negative, not positive.
Based on the analysis above, options a, b, c, and e are not likely to have a positive entropy change. Option d, I2(s) ----- I2(aq), is the only process that is likely to have a positive entropy change.