![]() ![]() ![]() However, when we get to the point that the solution is saturated, the pH is extremely high and there is very little hydronium left to react, so reaction (2) contributes much less, and the positive enthalpy change of reaction (1) dominates, making the reaction endothermic. In the case of infinite dilution (pH=7), both reactions are occurring, so the large negative enthalpy change of (2) results in a net negative enthalpy change, ie the reaction is exothermic. This reaction has a large negative enthalpy change. The van't Hoff equation shows clearly that the change in the equilibrium constant for a reaction with temperature is dependent on the enthalpy change of the reaction (and nothing else): Where Action Lab is correct and The Chemist is wrong is in the application of Le Chatelier's principle to heat. Pretty much all reactions go faster with higher temp, but in the case of reversible exothermic reactions, the reverse reaction increases in rate more quickly than the forward reaction, so the final equilibrium state has more reactant remaining. ![]() The Action lab is specifically incorrect in conflating kinetics (reaction rate) with thermodynamics (equilibrium). In my opinion, what I think That Chemist said was true, but correct me below. Sodium hydroxide when dissolving in water is exothermic, but it still gets more soluble as it gets hotter.Īnd not only that, but he had also said that dissolving sugar in water was a chemical change, even though it is strictly physical. "His rationale in the video-which is wrong is that because it's exothermic when it's dissolved, if you add heat it becomes less soluble." "All exothermic reactions slow down as it gets hotter."Ī video reacting to The Action Lab from That Chemist, in which he says : He also said that gases get less soluble in hot water than in cold water, which is true, by demonstrating it with a cold and hot soda can, noticing that the hot soda can bubbled up more violently than the cold one. Somewhat recently, The Action Lab made a video called "Why does this powder only dissolve in cold water?", saying the powder which was calcium acetate dissolves in cold water better than in warm water. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |