Which of the following salt solutions would coagulate the colloid solution formed when FeCl3 is added to NaOH solution, at the fastest rate?
Which of the following salt solutions would coagulate the colloid solution formed when FeCl3 is added to NaOH solution, at the fastest rate?
Show Hint
When determining coagulation rates:
• Apply the Schulze-Hardy rule: the higher the charge of the counter-ion, the stronger its coagulating power.
• For negatively charged colloids, focus on the cation with the highest charge and concentration.
10 mL of 0.1 mol dm–3 Ca3(PO4)2
10 mL of 0.2 mol dm–3 AlCl3
10 mL of 0.1 mol dm–3 Na2SO4
10 mL of 0.15 mol dm–3 CaCl2
The Correct Option is B
Solution and Explanation
- The colloidal solution formed when FeCl\(_3\) is added to NaOH is negatively charged.
- The coagulation of colloidal solutions is governed by the Schulze-Hardy rule: \textbf{the higher the valence of the oppositely charged ion, the greater its coagulating power.
Analysis:
Among the given options:
AlCl\(_3\) contains Al\(^{3+}\) ions, which have the highest coagulating power compared to other cations such as Ca\(^{2+}\) or Na\(^{+}\).
Therefore, the solution containing Al\(^{3+}\) ions (AlCl\(_3\)) will coagulate the colloidal solution at the fastest rate.
Final Answer: (1) 10 mL of 0.2 mol dm\(^{-3}\) AlCl\(_3\).
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