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There is some reading, but I don't think your answers will require a lot of writing, I'm trying to understand some concepts on osmotic pressure and vapor pressure and want to know if I'm thinking about them correctly, thanks for the help.
from my text book:
1)In terms of intermolecular forces what factors give rise to positive and negative deviations from Raoult's law(the vapor P of a solution is directly proportional to the mole fraction of solvent present Psolu= Xsolvent Psolvent)?
answer: if solute-solvent attraction > solvent-solvent and solute-solute attraction then there is a negative deviation from Raoult's Law , if solute-solvent attraction < solvent-solvent and solute-solute attraction then there is a positive deviation from Raoult's Law
I understand the question and the answer, but when I first read the question I looked at Xsolvent and thought that the larger the mole fraction of the SOLUTE is (in other words the more solute in a solution, which means smaller mole fraction of solvent) the smaller the vapor pressure of the solution would be, is that a correct generalization? (I know it doesn't answer the actual question from the book)
is it ok to generalize that the more solute in a solution, the lower the vapor pressure of that solution, and that the lower the vapor pressure of a solution, the more resistant it is to phase changes??
2) there is an apparatus that allows solid and liquid water to interact only through the vapor state, so ice is in one flask that has a long horizontal tube higher up connecting it to another flask with liquid water in it in a closed system, my book gives three experimental cases:
case 1: a T at which the vapor P of the solid is greater than that of the liquid, to cut the explanation short, it says vapor is released from the solid to try to achieve equilibrium, the liquid will absorb the vapor in an attempt to reduce the vapor P to its equilibrium value, ice will decrease and water will increase, no ice will remain, so this T must be above the mp of ice.
case2: a T at which the vapor P of the solid is less than that of the liquid, this is the opposite of the situation in case 1, in this case the liquid requires a higher P than the solid does to be in equilibrium w/the vapor, so the liquid will gradually disappear, and the amount of ice will increase, finally on solid will remain, which will achieve equilibrium w/the vapor, this T must be below the mp of ice.
case3: a T at which the vapor P of the solid and liquid are identical, this T represents the freezing point where both the solid and liquid states can exist.
I sort of understand case 1, at that T, if the vapor P of the solid is greater than that of the liquid, more solid is evaporating and the vapor is entering the liquid in the other flask and the level of water is increasing? or is the ice just melting in that very flask? or is the vapor traveling across the horizontal tube and increasing the water level of the other flask?
with case 2, water needs to be heated to evaporate, wouldn't that heat melt the ice? what I'm asking is that there can't be any condition where ice and liquid water are in the same place where water is evaporating but ice is not melting right? either way, I can't understand how water evaporating leads to ice building up? is the water turning into ice in that same flask or is the vapor going to the flask where the ice is and the ice is increasing?
and with case 3, I understand everything but why that T is a representation of the freezing point, could it also represent the melting point since they both have ice and liquid water present at the same time? so could it have been stated as "this T represents the melting point where both the solid and liquid states can exist" ?
3)solutions that have identical osmotic P's are said to be isotonic solutions, fluids administered intravenously must be isotonic w/body fluids, for ex, red blood cells are bathed in hypertonic solution, which is a solution having an osmotic P higher than that of the cell fluids, the cells will shrivel, this is called crenation, the opposite phenomenon, hemolysis, occurs when cells are bathed in a hypotonic solution, a solution w/an osmotic P lower than that of the cell fluids, the cell ruptures.
I understand, that water will want to diffuse (osmosis) from an area of higher concentration to an area of lower concentration, so if the cell is bathed in a hypertonic solution, there is a higher concentration of water inside the cell, and it will travel through the membrane out of the cell and the cell will shrivel, but from what I read I want to make a generalization about osmotic pressure, so if there is more solute in a solution (hypertonic solution), there is a greater osmotic P? always?, I imagine that the more solute a solution has, the more water will pass a permeable barrier and there will be a greater P (osmotic P) needed to stop the osmosis, so it always applies?
since osmotic pressure is the minimum P required to stop osmosis, and the osmotic P of the hypertonic solution is greater than the osmotic P of the fluid in the cell as my book says, it seems to rationalize the statement that the osmotic P of the hypertonic solution is greater I should think of it as the hypertonic solution is able to prevent osmosis of ITS fluid but allows water from the cell to come in? is the book statement worded strangely? that doesn't seem right to me, if the osmotic P is greater in a solution (the hypertonic solution), wouldn't it (by definition of osmotic P) prevent osmosis of fluid from the cell? (so I understand concentration gradients, but I'm trying to understand this by osmotic P and its a little strange) In the same way, I would think if the cells osmotic P is lower (when bathed in a hypertonic solution) then it would not be able to prevent osmosis of fluid INTO it, and it would rupture, not shrivel!
from my text book:
1)In terms of intermolecular forces what factors give rise to positive and negative deviations from Raoult's law(the vapor P of a solution is directly proportional to the mole fraction of solvent present Psolu= Xsolvent Psolvent)?
answer: if solute-solvent attraction > solvent-solvent and solute-solute attraction then there is a negative deviation from Raoult's Law , if solute-solvent attraction < solvent-solvent and solute-solute attraction then there is a positive deviation from Raoult's Law
I understand the question and the answer, but when I first read the question I looked at Xsolvent and thought that the larger the mole fraction of the SOLUTE is (in other words the more solute in a solution, which means smaller mole fraction of solvent) the smaller the vapor pressure of the solution would be, is that a correct generalization? (I know it doesn't answer the actual question from the book)
is it ok to generalize that the more solute in a solution, the lower the vapor pressure of that solution, and that the lower the vapor pressure of a solution, the more resistant it is to phase changes??
2) there is an apparatus that allows solid and liquid water to interact only through the vapor state, so ice is in one flask that has a long horizontal tube higher up connecting it to another flask with liquid water in it in a closed system, my book gives three experimental cases:
case 1: a T at which the vapor P of the solid is greater than that of the liquid, to cut the explanation short, it says vapor is released from the solid to try to achieve equilibrium, the liquid will absorb the vapor in an attempt to reduce the vapor P to its equilibrium value, ice will decrease and water will increase, no ice will remain, so this T must be above the mp of ice.
case2: a T at which the vapor P of the solid is less than that of the liquid, this is the opposite of the situation in case 1, in this case the liquid requires a higher P than the solid does to be in equilibrium w/the vapor, so the liquid will gradually disappear, and the amount of ice will increase, finally on solid will remain, which will achieve equilibrium w/the vapor, this T must be below the mp of ice.
case3: a T at which the vapor P of the solid and liquid are identical, this T represents the freezing point where both the solid and liquid states can exist.
I sort of understand case 1, at that T, if the vapor P of the solid is greater than that of the liquid, more solid is evaporating and the vapor is entering the liquid in the other flask and the level of water is increasing? or is the ice just melting in that very flask? or is the vapor traveling across the horizontal tube and increasing the water level of the other flask?
with case 2, water needs to be heated to evaporate, wouldn't that heat melt the ice? what I'm asking is that there can't be any condition where ice and liquid water are in the same place where water is evaporating but ice is not melting right? either way, I can't understand how water evaporating leads to ice building up? is the water turning into ice in that same flask or is the vapor going to the flask where the ice is and the ice is increasing?
and with case 3, I understand everything but why that T is a representation of the freezing point, could it also represent the melting point since they both have ice and liquid water present at the same time? so could it have been stated as "this T represents the melting point where both the solid and liquid states can exist" ?
3)solutions that have identical osmotic P's are said to be isotonic solutions, fluids administered intravenously must be isotonic w/body fluids, for ex, red blood cells are bathed in hypertonic solution, which is a solution having an osmotic P higher than that of the cell fluids, the cells will shrivel, this is called crenation, the opposite phenomenon, hemolysis, occurs when cells are bathed in a hypotonic solution, a solution w/an osmotic P lower than that of the cell fluids, the cell ruptures.
I understand, that water will want to diffuse (osmosis) from an area of higher concentration to an area of lower concentration, so if the cell is bathed in a hypertonic solution, there is a higher concentration of water inside the cell, and it will travel through the membrane out of the cell and the cell will shrivel, but from what I read I want to make a generalization about osmotic pressure, so if there is more solute in a solution (hypertonic solution), there is a greater osmotic P? always?, I imagine that the more solute a solution has, the more water will pass a permeable barrier and there will be a greater P (osmotic P) needed to stop the osmosis, so it always applies?
since osmotic pressure is the minimum P required to stop osmosis, and the osmotic P of the hypertonic solution is greater than the osmotic P of the fluid in the cell as my book says, it seems to rationalize the statement that the osmotic P of the hypertonic solution is greater I should think of it as the hypertonic solution is able to prevent osmosis of ITS fluid but allows water from the cell to come in? is the book statement worded strangely? that doesn't seem right to me, if the osmotic P is greater in a solution (the hypertonic solution), wouldn't it (by definition of osmotic P) prevent osmosis of fluid from the cell? (so I understand concentration gradients, but I'm trying to understand this by osmotic P and its a little strange) In the same way, I would think if the cells osmotic P is lower (when bathed in a hypertonic solution) then it would not be able to prevent osmosis of fluid INTO it, and it would rupture, not shrivel!
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