Question

The disperse phase in colloidal iorn (III) hydroxide and colloidal gold is positivley and regatively charged, respectively. Which of the following statement is NOT correct

• A. Magnesium chloride solution coagulates, the gold sol more readily than iron (III) hydroxide sol
• B. Sodium sulphate solution causes coagulation in both sols
• C. Mixing the sols has no effect
• D. Coagulating in both sols can be brought about by electrophoresis

Answer 1

The correct option is C Mixing the sols has no effect

As dispersed phase in colloidal iron (III) hydroxide is positively charged, it can be coagulated by negative ions.

Dispersed phase in colloidal gold sol is negatively charged, it can be coagulated by positive ions.

In Mg chloride, positive cation $M{g}^{+2}$ coagulates iron (III) hydroxide and $C{l}^{-}$ ion coagulates colloidal gold sol. As cation has more charge than anion, it coagulates fast.

Also, sodium sulphate solution contains both cation and anion. So, it can coagulate both sols.

Coagulation in both sols can be brought about by electrophoresis.

But when we mix them together, due to opposite charge colloidal sol they coagulate.