Colloids

1. Understand the Concept of Zeta Potential
The zeta potential is the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed phase. In other words, it is the electrical potential difference between the electrical double layer of a colloidal system. The electrical double layer consists of a fixed layer (ions strongly bound to the particle surface) and a diffuse layer (ions distributed in the surrounding medium).

2. Analyze the given options

- (A) Potential required to bring about coagulation of a colloidal sol: While zeta potential is related to the stability of a colloid and its tendency to coagulate, this definition is not the most accurate description of zeta potential itself.

- (B) Potential required to give the particle a speed of 1 cm S^-1: This definition has no relationship to the zeta potential.

- (C) Potential difference between fixed charged layer and the diffused layer having opposite charges: This is the correct definition of zeta potential. It describes the potential difference within the electrical double layer.

- (D) Potential energy of the colloidal particles: Zeta potential is a potential difference, not the potential energy of the particles themselves.

3. Conclusion
The best definition of zeta potential among the options provided is (C).

Final Answer:
(C) Potential difference between fixed charged layer and the diffused layer having opposite charges

1. Understand the Hardy-Schulze Rule
The Hardy-Schulze rule states that the coagulating power of an electrolyte is directly proportional to the valency of the ions carrying the charge opposite to that of the colloidal solution. In simpler terms, the greater the charge on the ion that neutralizes the colloid, the more effective it is at causing coagulation. This means that a smaller amount of the electrolyte with the higher charge is needed for coagulation.

2. Determine the charge of the colloidal particles
The question states that "colloidal particles move more towards the anode." This implies that the colloidal particles are negatively charged since they are attracted to the positive electrode (anode).

3. Identify the effective ions for coagulation
Since the colloidal particles are negatively charged, the positive ions (cations) of the electrolytes will be effective in causing coagulation. The electrolytes are:

- NaCl → + (cation is with a +1 charge)
- → + (cation is with a +2 charge)
- → + (cation is with a +3 charge)

4. Apply the Hardy-Schulze Rule to determine the order of coagulating power
According to the Hardy-Schulze rule, the coagulating power increases with the charge of the cation. Therefore, the order of coagulating power is:

> >

Since the question asks for "The amount of electrolytes... required to coagulate the given colloid," we need to consider that the amount of electrolyte needed will be inversely proportional to the coagulating power. That is, the higher the charge of the ion, the LESS of the electrolyte needed. Thus, the amount required will be in the opposite order.

Therefore, the order of the amount of electrolyte required is:

NaCl > >

5. Compare with the given options
Comparing the derived order with the options, we find that it matches option (A).

Final Answer:
(A) NaCl > >