Question

If starch, glucose and NaCl are soaked in the dialysis tubing , will there be a difference between the beginning and after 15minutes?

Answer 1

Also, is it salt is most permeable, then glucose, then starch?

Answer 2

You're right about the order of permeability. The smaller molecules can diffuse through the semi-permeable membrane and reach equilibrium more readily than the larger ones.

But what that equilibrium actually is depends on the concentration gradient between the solution and inside the dialysis bag...

Answer 3

what about the first question? Will there be a difference if you leave it for a while compare to the beginning when everything is juz added to the dialysis tubing?

Answer 4

If you put solutions containing the same concentration table salt, glucose and starch in different bags and place the bags in water (i.e., 0M) solution, then the bag with salt will contain more water after 15 than the bag with glucose, which will contain more than the bag with startch.

Sorry for the run on sentence.

Answer 5

the lab i'm doing is 1% starch 10% glu and 5% nacl
so does it make a difference?

and plus all of them are put in 1 dialysis tubing , so cant really compare the water flow among them

Answer 6

What an odd lab.

Yes, there should be a difference. Water should flow down its concentration gradient into the dialysis tube, so it should weigh more at the end than at the start.

Um, that said, that is an absolutely terrible lab project. So much can go wrong in terms of drying the bags, scale malfunctions, etc. that you should be prepared for big margins of error.

Answer 7

the lab itself is confusing...first have to find out positive test, and soak everything in the dialysis tubing, after transfer it to a beaker, get some samples and then test for the color change.. like that...

and btw, will some of the glucose remain in the tubing? This is just a passive transport right? so glucose cant really go thru

Answer 8

The main point about dialysis bags is that only water molecules can fit through the pores. So all of the glucose molecules will remain in the tubing; it's just that more water will have entered, so the relative proportion of glucose molecules to water molecules will have decreased. That is, the solutions in the tube will be more dilute.

Answer 9

oh, so that means only salt can pass over, glucose and starch will remain in the tubing? then there is not much difference between starch and glucose?

Answer 10

Whether salt can pass through the pores depends on what kind of dialysis tubing you're using. Typically, only water can pass through, but if you're using bags with large pores, then maybe salt can go through too.

Glucose and stach can't. Glucose is a monosaccharide. Starch is a great big polysaccharide.

By the way, congrats, Superstar. ;D

Answer 11

oh ok thanks

and yea, superstar now hahah :D