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23 Cards in this Set

  • Front
  • Back
157. Define the frictional force (F) acting on a molecule with
velocity v in an aqueous environment?
F=-f·v, where f is the form factor.
158. What is the relationship between the absolute
temperature (T) and the average kinetic energy of a
Minimum Requirement Questions (2005/06) 8
molecule (Ekin) in a system containing monatomic gas in
thermal equilibrium?
Ekin = 3/2 kT
where k is the Boltzmann constant.
159. What is diffusion?
Net flow of material propelled by Brownian motion due to
a gradient of the chemical potential.
160. 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.
161. What is the unit of diffusion constant?
[D] = m2/s
162. Give the average squared displacement and averate
squared rotation of a particle with diffusion constant D
and rotational diffusion constant Drot, respectively!
x^2 = Dt Θ^2 = 2Drot t
where t is time, and x2 and Θ2 is the average squared
displacement and rotation, respectively.
163. Write Fick's first law and interpret the constants and
physical quntities!
dm/dt = -DA(dc/dx)

dm quantity of material is transported through surface A
in time dt by a concentration gradient dc/dx, D is the
diffusion constant
164. How does the diffusion constant (D) depend on
temperature (T) and the radius of the molecule (r) ?
165. Write down the equation describing the relationship
between the diffusion constant (D) and the form factor
where k is the Boltzmann constant and T is the absolute
166. Which parameters tend toward spatial equilibration
during a diffusion process?
The chemical potentials of the components.
167. What is pH?
The negative logarithm with base 10 of the molar
concentration of hydrogen ions: pH=-lg[H+]
168. What is the permeability constant?
The permeability constant is the amount of material
transported through the membrane per unit surface in
unit time due to unit concentration difference.
169. Give the equation describing the amount of material
transported through a membrane due to a concentration
dm = −k ⋅ A⋅Δc ⋅ dt
where dm is the amount of material transported through
membrane surface A during time dt as an effect of Δc
concentration difference, k is the membrane
170. Write down van't Hoff's law!
Posm = RTc, where
Posm - osmotic pressure,
R is theuniversal gas constant,
T is absolute temperature,
c is the molar concentration of the material in solution.
171. 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
172. What is osmotic pressure?
It is the pressure generated by the flow of the solvent
molecules through a semipermeable membrane which is
able to compensate the solvent flow.
173. What is the average speed at which the heart pumps the
blood into the aorta?
20-40 cm/s
174. What is the average amount of blood pumped out of the
heart during a single contraction?
70-90 mL
175. What components does the work of the heart consist of?
Volumetric and kinetic work.
176. Describe in words the law of Bernoulli!
The sum of the statical, dynamic and gravitational
(hydrostatic) pressures is constant.
177. What kind of chemical bonds does electromagnetic
waves of a microwave oven disrupt?
The hydrogen bonds of water.
178. Why does a microwave oven boils water?
Because water is able to absorb the microwaves in the
oven since the energy of the hydrogen bonds between
water molecules is approximately the same as the
energy of a microwave photon.
179. What is the relationship between the number of bacteria
and time under optimal conditions?
N is the number of bacteria at time t,
N0 is the initial number of bacteria at t=0,
T is the generation time.