What must be true for a substance to dissolve in water?
A. The entropy term must be positive.
B. The enthalpy and entropy terms must combine for a favored reaction.
C. The free energy change of dissolving must be positive.
D. The energy required to break bonds apart must be greater than the energy released from the substance reacting with the solvent.
I think the answer could be B because in order for a reaction to occur it must be a favored reaction
I agree and for that reason. D is the reverse for a true statement, the negative is true for c. A is true but doesn't go far enough but could be negative and dissolution could still take place.
b is right on apex
Hmm, let's see. Well, if I were a substance trying to dissolve in water, I would need a few things. First, I would need some positive entropy to keep things lively. So, option A seems like a good start. But, I'm a little greedy and want more. I also need the enthalpy and entropy terms to join forces and work together like a power duo to create a favorable reaction. So, option B sounds like a good second choice. As for option C, a positive free energy change might discourage me a bit. Lastly, option D suggests that the energy needed to break bonds apart should be greater than the energy released when I react with the solvent. Well, that sounds like a lot of hard work, so I'll pass on that one. So, considering all these options, I'll go with B. The enthalpy and entropy terms must combine for a favored reaction.
To determine what must be true for a substance to dissolve in water, we need to consider the concepts of entropy, enthalpy, and free energy change.
A. The entropy term must be positive: Entropy refers to the degree of disorder or randomness in a system. In general, substances tend to dissolve in water if the entropy of the system increases. When a substance dissolves, the particles become more dispersed, leading to increased randomness, which corresponds to a positive change in entropy.
B. The enthalpy and entropy terms must combine for a favored reaction: Enthalpy refers to the heat energy of a system. For dissolution to occur, the combined effect of the enthalpy and entropy changes must favor the reaction. Both favorable enthalpy and entropy changes can promote solubility, but the specific combination will depend on the substance and its interactions with water.
C. The free energy change of dissolving must be positive: Free energy change is a measure of the spontaneity of a reaction. For a substance to dissolve in water spontaneously, the free energy change should be negative. This means that the energy required to break the bonds of the solid substance and the energy released from the substance interacting with water must be favorable. Therefore, the correct statement is that the free energy change of dissolving must be negative, not positive.
D. The energy required to break bonds apart must be greater than the energy released from the substance reacting with the solvent: This statement is incorrect. If the energy required to break the bonds of the substance is greater than the energy released from the substance reacting with the water, the overall process would not be energetically favorable, and the substance would have a lower likelihood of dissolving.
So, the correct answer is A. The entropy term must be positive, as an increase in entropy generally promotes the dissolution of a substance in water.