The disperse phase in colloidal iron (III) hydroxide and colloidal gold is positively and negatively charged, respectively, which of the following statements is NOT correct?
- (A)magnesium chloride solution coagulates, the gold sol more readily than the iron (III) hydroxide sol.
- (B)sodium sulphate solution causes coagulation in both sols
- (C)mixing the sols has no effect✓ Correct
- (D)coagulation in both sols can be brought about by electrophoresis
Answer: (C)
Solution
Iron(III) hydroxide sol carries a positive charge while gold sol carries a negative one, and that opposition is the key. Because the two sols bear opposite charges, pouring them together lets each neutralise the other and brings about mutual coagulation, so to say that mixing them has no effect is plainly wrong. The remaining statements hold up: a salt coagulates the negative gold sol especially well, a salt can coagulate the positive iron sol, and electrophoresis drives the charged particles to the electrodes and discharges them in either case.
JEE Main · 2005 · 08 May 2005 · Offline · Single correct option