coconut64
Badges: 16
Rep:
?
#1
Report Thread starter 5 years ago
#1
What is the difference between solute potential and solute concentration? I get that the lower the solute potential, the lower the water potential but what about solute concentration? Thanks
0
reply
zombiejon
Badges: 9
Rep:
?
#2
Report 5 years ago
#2
Inverse relationship, if I remember correctly.

High [solute] = low solute potential.
0
reply
coconut64
Badges: 16
Rep:
?
#3
Report Thread starter 5 years ago
#3
(Original post by zombiejon)
Inverse relationship, if I remember correctly.

High [solute] = low solute potential.
Why would that be the case? I always thought high solute concentration =high solute potential... Thanks
0
reply
zombiejon
Badges: 9
Rep:
?
#4
Report 5 years ago
#4
(Original post by coconut64)
Why would that be the case? I always thought high solute concentration =high solute potential... Thanks
It doesn't relate to to the potential of solutes to dissociate from the solution. Rather, solute potential is one of the factors in determining water potential.

Ψ = Ψs + Ψp

Ψs is the solute/osmotic potential (interchangeable terms).

Generally, Ψs indicates the potential of water to move from a hypotonic to hypertonic solution.

Ψs of pure water is considered 0. Adding solutes to a solution results in an increasing solute concentration, and a decreasing solute potential, as water is less likely to leave the system when separated from pure water by a semi-permeable membrane.

Going a bit further into chemical equations to provide a bit more background:
Ψs = -iMRT
M = molarity of solute
i = van 't Hoff factor (determined by dissociation of solute)
R = ideal gas constant
T = temperature

i for glucose is 1 (as there is no dissocation)
i for NaCl is 2 (Na and Cl separate completely in water)
i for CaCl2 is 3 (Ca and Cl separate completely, resulting in 3 particles in the solution)

Overall, increasing the number of solutes results in an increasingly negative solute potential.
0
reply
coconut64
Badges: 16
Rep:
?
#5
Report Thread starter 5 years ago
#5
(Original post by zombiejon)
It doesn't relate to to the potential of solutes to dissociate from the solution. Rather, solute potential is one of the factors in determining water potential.

Ψ = Ψs + Ψp

Ψs is the solute/osmotic potential (interchangeable terms).

Generally, Ψs indicates the potential of water to move from a hypotonic to hypertonic solution.

Ψs of pure water is considered 0. Adding solutes to a solution results in an increasing solute concentration, and a decreasing solute potential, as water is less likely to leave the system when separated from pure water by a semi-permeable membrane.

Going a bit further into chemical equations to provide a bit more background:
Ψs = -iMRT
M = molarity of solute
i = van 't Hoff factor (determined by dissociation of solute)
R = ideal gas constant
T = temperature

i for glucose is 1 (as there is no dissocation)
i for NaCl is 2 (Na and Cl separate completely in water)
i for CaCl2 is 3 (Ca and Cl separate completely, resulting in 3 particles in the solution)

Overall, increasing the number of solutes results in an increasingly negative solute potential.
I was given this question: Describe and explain the effects of placing animal and plant cells in solutions of differing solute concentration . I don't get this because the question asks about solute concentration but in the markscheme, it only mentions solute potential. How can you relate them then?

Also, when the water leaves the cell into the external solution, can you only say that the solution is hypotonic to the cell? Because that's why they described it in the textbook.. thanks
0
reply
zombiejon
Badges: 9
Rep:
?
#6
Report 5 years ago
#6
(Original post by coconut64)
I was given this question: Describe and explain the effects of placing animal and plant cells in solutions of differing solute concentration . I don't get this because the question asks about solute concentration but in the markscheme, it only mentions solute potential. How can you relate them then?
I would break this question down into 3 sections: hyper, iso, and hypotonic. See below for how I would word it.

Also, when the water leaves the cell into the external solution, can you only say that the solution is hypotonic to the cell? Because that's why they described it in the textbook.. thanks
If the external solution is hypotonic to the cell, it means it has a lower solute concentration, thus a higher solute potential. As solute potential plays a part in determining water potential, the external solution has a higher water potential than the cell, therefore water is more likely to flow into the cell.

If the external solution is hypertonic to the cell, it means it has a higher solute concentration, thus a lower solute potential. As solute potential plays a part in determining water potential, the cell has a higher water potential, therefore water is more likely to leave the cell for the external media.

Usually, mentioning key words would result in full marks, as long as it is used and explained correctly.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Are you tempted to change your firm university choice on A-level results day?

Yes, I'll try and go to a uni higher up the league tables (9)
37.5%
Yes, there is a uni that I prefer and I'll fit in better (2)
8.33%
No I am happy with my choice (13)
54.17%
I'm using Clearing when I have my exam results (0)
0%

Watched Threads

View All
Latest
My Feed