The correct answer is (2) D only.
The most effective electrolyte for the coagulation of a colloidal solution is the one that can neutralize the charges on the colloidal particles to the greatest extent. This is because coagulation occurs when the colloidal particles are no longer repelled from each other and can start to aggregate.
In the case of the \(\text{Fe}_2\text{O}_3 \cdot \text{H}_2\text{O} / \text{Fe}^{3+}\) colloidal solution, the colloidal particles are positively charged. Therefore, the most effective electrolyte for coagulation will be one that contains a highly negatively charged ion.
Of the options given, only potassium ferrocyanide, \(\text{K}_4[\text{Fe}(\text{CN})_6]\), contains a highly negatively charged ion, the hexacyanoferrate(II) ion, \([\text{Fe}(\text{CN})_6]^{4-}\). This ion has a charge of -4, which is much higher than the charge of any of the other ions in the options.
Therefore, potassium ferrocyanide, \(\text{K}_4[\text{Fe}(\text{CN})_6]\), is the most effective electrolyte for the coagulation of the \(\text{Fe}_2\text{O}_3 \cdot \text{H}_2\text{O} / \text{Fe}^{3+}\) colloidal solution.
The other options are not as effective for coagulation because they contain ions with lower charges. For example, silver chloride, \(\text{AgCl}\), and potassium chloride, \(\text{KCl}\), both contain ions with a charge of -1. Magnesium chloride, \(\text{MgCl}_2\), contains ions with a charge of -2. Ferric chloride, \(\text{FeCl}_3\), contains ions with a charge of +3.
Therefore, the correct answer is (2) D only. |
