Aluminum hydroxide forms a positively charged sol. Which of the following ionic substances should be most effective in coagulating the sol?
NaCl
CaCl2
Fe2(SO4)3
K3PO4
The idea behind coagulating sols is to use those salts that have the highest + and - charges and the most ions.
To determine which ionic substance would be most effective in coagulating the sol, we need to consider the charges of the ions present in the substances. Coagulation refers to the process of clumping together and precipitating suspended particles in a solution.
In this case, aluminum hydroxide forms a positively charged sol. So, we need an ionic substance that contains negatively charged ions to neutralize the positive charges of the sol particles and cause coagulation.
Looking at the options:
- NaCl: Sodium chloride dissociates into sodium ions (Na+) and chloride ions (Cl-). While chloride ions are negatively charged, they are less effective in neutralizing the positive charges of aluminum hydroxide compared to other options.
- CaCl2: Calcium chloride dissociates into calcium ions (Ca2+) and chloride ions (Cl-). Since calcium ions have a higher charge than sodium ions, they are more effective in neutralization than NaCl.
- Fe2(SO4)3: Iron(III) sulfate dissociates into iron(III) ions (Fe3+) and sulfate ions (SO42-). Since the charge of the iron(III) ions is higher than calcium ions, Fe2(SO4)3 would be more effective in coagulating the sol than CaCl2.
- K3PO4: Potassium phosphate dissociates into potassium ions (K+) and phosphate ions (PO43-). While phosphate ions are negatively charged, they are not as effective as sulfate ions in neutralizing the positive charges of aluminum hydroxide.
Therefore, based on the charges of the ions present, Fe2(SO4)3 would be the most effective ionic substance in coagulating the aluminum hydroxide sol.