Hello!
Aufbau's principle states that electrons fill up orbitals with the same spin first, then double up.
Like they go all up spin first, then fill up the orbitals with down spin.
Is the same true in reverse? That electrons with the same spin would leave first, or would the rule not apply here?
Thank you
I thought I understood this concept till I started thinking about it.
Suppose we have a substance M, which when dissolved in water absorbs heat and the temperature drops.
What is the system and what is the surrounding?
Would the system be the substance + water, (the solution), or would it be just the substance?
This comes from the concept that in an endothermic reaction, the system takes in heat from the surroundings. Thus, when the substance gains energy, it is gaining it FROM the water, so wouldn't that make the water a surrounding? I would think of it this way because the chemical reaction with water would give chemical energy (bonds etc) to the substance.
If we were to consider the entire solution as the system. Then where is the system getting the energy from? The reaction is clearly endothermic, the energy changes only happened from the thermal exchange between the substance and the solution, and the heat was trapped within the intermolecular forces and bonds, thus the temperature went down. The system didn't actually take in heat from the surroundings.
Please correct me if any of this is wrong, and I want to know which interpretation would be correct, why, and how I can identitfy the system and surroudnings for other questions. Examples would be appreciated. Thank you.
Hello!
I had a question that went something like
ΔH soln of KCL in water is 14kJ/mol. if 3 mols of KCL are dissolved, find the amount of energy absorbed by KCL. Temperature decreases
I know you solve this by simply multiplying 14 by 3 and boom thats the answer.
However, what does ΔH soln even mean? Does it mean the change in enthalphy of the solution per 1 mol of the reaction (KCL + H20), or does it mean change in enthalpy per 1 mol of KCL that reacts?
Thus, by that interpretation, it is saying, for 1 one mol of KCL, the entire solution increases by 14 kJ of heat.
However, why do we use 3 mols of KCL? Is it because it is the limiting reactant?
Additionally, what if water was the limiting reactant, would you use mols of water for that reaction then?
Could there be a question that simply says "ΔH soln is 14kJ/mol" and we have to assume that means 14kJ/mol per mol of solute? Or would it mean per 1 mol of reaction, the solution gains 14kJ of heat.
In essense, I am having trouble understanding the notation of ΔH soln, and I keep finding conflicting answers online.
Any help would be greatly appreaciated
Thank you.