Question

Calculate the zeta potential of a colloidal particle, given that the particle has a charge of -3.2 × 10^-19 C, a diameter of 250 nm, and is suspended in a solution with a dielectric constant of 78.3.

Answer 1

To calculate the zeta potential of a colloidal particle, we can use the following formula:Zeta potential    =  q *   /   * r where:q = charge of the particle  -3.2  10^-19 C  = viscosity of the solution  we don't have this value, but we can assume it's water at room temperature, which has a viscosity of ~8.9  10^-4 Pas  = dielectric constant of the solution  78.3  multiplied by the vacuum permittivity constant  8.854  10^-12 C/Nm r = radius of the particle  half of the diameter, so 125 nm or 125  10^-9 m First, let's calculate : = 78.3 * 8.854  10^-12 C/Nm = 6.93  10^-10 C/NmNow, we can calculate the zeta potential: =  -3.2  10^-19 C * 8.9  10^-4 Pas  /  6.93  10^-10 C/Nm * 125  10^-9 m  =  -2.848  10^-22 CPas  /  8.66  10^-20 C/N   -32.9 mVThe zeta potential of the colloidal particle is approximately -32.9 mV.