17 Questions
Which technique is used to measure the electrophoretic mobility of charged particles?
Electrophoresis
What is the streaming potential technique used to estimate?
Zeta Potential
According to the text, who first conceived the electric double layer model?
Helmholtz
What is the general assumption about the surface in the electric double layer model?
The surface is flat and extends infinitely.
The point at which the zeta potential is zero is called the ______ point
Isoelectric
Electrophoretic mobility is measured by observing the velocities of charged particles under a potential gradient and in the absence of ______ flow.
convective
The streaming potential technique involves forcing a solution through a packed bed of particles at whose opposite ends are placed ______.
electrodes
What is the formula used to calculate the zeta potential in electrophoresis?
$z = 4\pi \mu V \times 9 \times 10^4$ Volts
What is the formula used to estimate the zeta potential in the streaming potential technique?
Not provided in the text.
What are the units of solution viscosity in the SI system?
poise (10^-1 N.s.m^-2)
What is the process that usually precedes the dissociation of surface functional groups?
The adsorption of water molecules to produce a hydroxylated surface.
What is the term used to describe the charged surface produced after the protonation or deprotonation of surface hydroxyls?
Charged surface: MOH (surf) + H+ = MOH2+(surf) or MOH (surf) = MO- (surf) + H+ (for oxides)
What is the term used to describe the charged surface produced after the protonation or deprotonation of the thiol group (SH) on sulphides?
Charged surface: SH (surf) +H+ = SH2+ (surf) or SH (surf) = S- (surf) + H+
According to the text, what are the general assumptions used in developing the electrical double layer model?
- the surface is flat, extends infinitely and is uniformly charged 2. the ions in the diffuse part of the double layer are point charges and obey the Boltzmann's point charge distribution as follows; n+ = no exp[ -zey ] RT n- = no exp[ +zey ] RT where n+, n-- are the number of positive and negative ions per unit volume at points where the potential is ψ (ie. zeψ is the electric potential energy), n○ is the bulk concentration of each ion species, z is the charge number and e is electronic charge.
What is the 'thickness' of the diffuse layer usually estimated by?
The 'thickness' of the diffuse layer is usually estimated by 1/κ where 1/κ = 3.04 x 10-10(Cz^2)^(-1/2) (m) at 25°C and C is the concentration of the electrolyte in mol.dm^-3 is often referred to as the Debye-Hückel thickness parameter.
What are counter ions and how are they adsorbed?
Counter ions are ions that possess no special affinity for the surface and therefore are adsorbed by electrostatic attraction.
What is the total double layer potential and how is it defined?
The total double layer potential, Ψo, is defined as the potential difference between the surface and the bulk of the solution.
Test your knowledge on the dissociation of surface functional groups and the role of water molecules in producing charged surfaces. This quiz will cover topics such as hydroxylation, protonation, and deprotonation of surface hydroxyls. Explore the processes involved in oxide and sulphide surfaces and enhance your understanding of this important phenomenon.
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