Water 1
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Questions and Answers

What happens to the chemical potential of a solute as its concentration increases?

  • It increases. (correct)
  • It remains constant.
  • It decreases significantly.
  • It fluctuates randomly.

    • In which direction does diffusion occur according to chemical potential?

  • From high chemical potential to low chemical potential. (correct)
  • Randomly in all directions.
  • From low chemical potential to high chemical potential.
  • Only in the presence of an impermeable barrier.

    • What is the significance of reaching equilibrium in the context of solute diffusion?

  • It results in an increasing concentration gradient.
  • It leads to the formation of new solutes.
  • It means no net movement of solute occurs. (correct)
  • It indicates continuous movement of solute.

    • What does Fick's Law describe in relation to diffusion?

    <p>The rate of diffusion based on concentration gradient.</p> Signup and view all the answers

    Which of the following correctly describes absolute temperature?

    <p>It is measured in Kelvin.</p> Signup and view all the answers

    What is the unit of pressure historically used by plant physiologists to discuss water movement?

    <p>Atm</p> Signup and view all the answers

    What is the relationship between pressure and energy in the context of water movement?

    <p>Energy per volume equates to pressure.</p> Signup and view all the answers

    What happens to the chemical potential (Ψ) of water when a solute is dissolved in it?

    <p>It decreases.</p> Signup and view all the answers

    What units can pressure be expressed in, aside from MPa, when discussing energy?

    <p>J m-3</p> Signup and view all the answers

    What is the effect of increasing solute concentration on water potential (Ψ)?

    <p>It becomes more negative.</p> Signup and view all the answers

    In which direction does water typically diffuse in relation to solute concentration?

    <p>From lower solute to higher solute.</p> Signup and view all the answers

    What does the presence of solutes do to the organization of water molecules?

    <p>Creates hydration shells.</p> Signup and view all the answers

    How is potential energy affected when a solute is dissolved in water?

    <p>It is diminished.</p> Signup and view all the answers

    What is the driving force behind the diffusion of water across a semi-permeable membrane?

    <p>Gradient of chemical potential</p> Signup and view all the answers

    In which direction does water move during osmosis?

    <p>From lower solute concentration to higher solute concentration</p> Signup and view all the answers

    What does the symbol Ψ represent in the context of water potential?

    <p>The chemical potential of water</p> Signup and view all the answers

    At standard atmospheric pressure, what is the water potential (Ψ) of pure H2O?

    <p>0 MPa</p> Signup and view all the answers

    What is the main concept that dictates the movement of both solutes and water across membranes?

    <p>Concentration gradient</p> Signup and view all the answers

    If a cell is placed in a solution with higher sucrose concentration compared to the inside of the cell, what will happen?

    <p>Water will leave the cell</p> Signup and view all the answers

    How does the movement of water compare to the movement of solute in an osmosis scenario?

    <p>Water moves in the opposite direction to solute</p> Signup and view all the answers

    What is the significance of a semi-permeable membrane in the context of osmosis?

    <p>It restricts the passage of solute while allowing water to flow</p> Signup and view all the answers

    What is the equation representing water potential (Ψ)?

    <p>Ψ = ΨS + ΨP + ΨM</p> Signup and view all the answers

    Which statement accurately describes solute potential (ΨS)?

    <p>ΨS is always negative and has a maximum value of 0 MPa.</p> Signup and view all the answers

    What does the 'i' in the van't Hoff equation represent?

    <p>Ionization constant of the solute</p> Signup and view all the answers

    Which of the following statements is true regarding the van't Hoff equation?

    <p>It is applicable only for dilute, ideal solutions.</p> Signup and view all the answers

    In the context of solute potential, what is the effect of adding solute to pure water?

    <p>It decreases the chemical potential of the water.</p> Signup and view all the answers

    Which value represents the maximum solute potential (ΨSmax)?

    <p>0 MPa</p> Signup and view all the answers

    What is the primary reason for the negative value of solute potential (ΨS)?

    <p>It reflects the presence and influence of solutes on water potential.</p> Signup and view all the answers

    What is the relationship between molality and molarity for dilute solutions?

    <p>Molality and molarity are typically the same.</p> Signup and view all the answers

    What happens to red blood cells in a hypotonic solution?

    <p>They will burst due to increased water intake.</p> Signup and view all the answers

    What defines a selectively permeable membrane?

    <p>A membrane that allows only certain substances to pass through.</p> Signup and view all the answers

    How do plant cells differ from red blood cells regarding osmotic pressure?

    <p>Plant cells are pressurized and have a cell wall to withstand osmotic pressure.</p> Signup and view all the answers

    In terms of solute concentration, how is osmotic movement defined?

    <p>From higher solute concentration to lower solute concentration.</p> Signup and view all the answers

    What happens to plant cells in a hypertonic solution?

    <p>They become plasmolyzed and may lose turgor pressure.</p> Signup and view all the answers

    What is the term used to describe the rigidity and pressure in plant cells?

    <p>Turgor.</p> Signup and view all the answers

    What can occur if sufficient water enters a red blood cell?

    <p>It will expand until lysis occurs.</p> Signup and view all the answers

    Which of the following best describes the condition of red blood cells in isotonic solutions?

    <p>They are in a state of equilibrium.</p> Signup and view all the answers

    Study Notes

    Chemical Potential (µ) and Diffusion

    • Chemical potential (µ) describes a substance's tendency to move. It's calculated using µ = RT ln c (J/mol), where R is the gas constant, T is absolute temperature (K), and c is solute concentration.
    • Higher concentration equates to higher chemical potential.
    • Diffusion follows a chemical potential gradient: high µ to low µ.
    • Fick's Law sufficiently explains solute diffusion; chemical potential isn't always necessary for these calculations.

    Water Diffusion and Osmosis

    • Water movement is driven by chemical potential gradients, similar to solutes, though the formalism differs.
    • Osmosis is water's diffusion across a semipermeable membrane between solutions of differing concentrations (and thus chemical potentials). It's a specific type of water diffusion.
    • The driving force for water diffusion remains the same regardless of a membrane's presence.

    Water Potential (Ψ)

    • Water potential (Ψ) quantifies water's chemical potential, measured relative to pure water at standard atmospheric pressure. Units are typically MPa.
    • Pure water at standard atmospheric pressure has Ψ = 0 MPa (by definition).
    • Water flows from high Ψ to low Ψ (down a Ψ gradient).
    • Pressure units (MPa) represent energy (energy/volume = pressure), even though the baseline units are technically J/mol.

    Effects of Solutes on Water Potential

    • Dissolving solutes in water decreases water's chemical potential (Ψ) because water molecules become more ordered around solute molecules (lower entropy).
    • Water with dissolved solutes has Ψ < 0 MPa at atmospheric pressure. Greater solute concentration means a greater negative Ψ.

    Water Relations in Cells

    • In red blood cells (lacking cell walls), water movement via osmosis can cause bursting if the internal solute concentration is lower than the external concentration.
    • Plant cells, with cell walls, exhibit turgor (rigidity and pressure) due to water influx, preventing bursting, even under osmotic pressure.

    Components of Water Potential

    • Water potential (Ψ) is a sum of its components: Ψ = ΨS + ΨP + ΨM
      • ΨS: Solute potential (osmotic potential), always negative, affected by solute concentration.
      • ΨP: Pressure potential
      • ΨM: Matric (matrix) potential

    Solute Potential (ΨS)

    • ΨS reflects the impact of solutes on water potential, not the solute's potential.
    • Calculated using a modified van't Hoff equation: ΨS = -ciRT, where:
      • c: solute concentration (molality)
      • i: ionization constant (1 for non-ionized molecules, varies for others)
      • R: universal gas constant
      • T: temperature (K)
    • This equation is accurate only for dilute, ideal solutions. Molality and molarity are almost interchangeable in dilute solutions.

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    Description

    Test your understanding of chemical potential, diffusion, and osmosis with this quiz. Explore how these concepts govern the movement of substances and how Fick's Law applies to diffusion. Delve into the specifics of water potential and its implications in various solutions.

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