12 Diffusion Flashcards
What is the definition of chemical potential?
Chemical potential of a substance is the Gibbs free energy of one mole of the given substance, i.e. the chemical potential of a substance gives by how much the Gibbs free energy of a thermodynamic system increases when one mole of the given substance is added to the system (at constant temperature and pressure).
Define the frictional force (Ff) acting on a molecule with velocity v in an aqueous environment
Ff=-fv, where f is the form factor.
What is the relationship between the absolute temperature (T) and the average kinetic energy of a molecule (Ekin) in a system containing monatomic gas in thermal equilibrium?
Ekin = 3/2 kT , where k is the Boltzmann constant.
What is diffusion?
Net flow of material propelled by Brownian motion due to a gradient of the chemical potential.
What is the physical meaning of the diffusion constant?
The diffusion constant (D) is the amount of material transported through unit surface area in unit time at a unit concentration gradient. It characterizes the mobility of molecules.
What is the unit of diffusion constant?
[D] = m2/s
Give the average squared displacement of a particle with diffusion constant D!
Deltax2 = 2Dt
where t is time, and Delta x2
displacement.
Give the average squared displacement of a particle with diffusion constant D!
Deltax2 = 2Dt
where t is time, and Delta x2
displacement.
Write Fick’s first law and interpret the constants and physical quantities!
Iv = -DA Δc/Δx
Iv is the quantity of material transported through the surface A per unit time by a concentration gradient Δc/Δx, D is the diffusion constant
How does the diffusion constant (D) depend on temperature (T) and the radius (r) of a spherical molecule?
D - T/r
. Write down the equation describing the relationship between the diffusion constant (D) and the form factor (f)!
D = kT/f
where k is the Boltzmann constant and T is the absolute temperature.
Which parameters tend toward spatial equilibrium during a diffusion process?
The chemical potentials of the components.
Which parameters tend toward spatial equilibrium during a diffusion process?
The chemical potentials of the components.
What is osmosis?
Flow of the solvent to a concentrated solution from the more dilute one, if the two compartments are separated by a semipermeable membrane. This material flow decreases the concentration gradient between the two solutions
What is osmosis?
Flow of the solvent to a concentrated solution from the more dilute one, if the two compartments are separated by a semipermeable membrane. This material flow decreases the concentration gradient between the two solutions
