Subject: Physical Chemistry · Chapter: Surface Chemistry · Topic: Surface Chemistry – General · Exam: CSIR-NET DEC 2011 · Marks: 2 · Difficulty: Medium
Flocculation value of $\mathrm{K_2SO_4}$ is much less than that of KBr for Sol A. Floccultion value of $\mathrm{CaCl_2}$ is much less than that of NaCl for Sol B. Which of the following statements is correct?
(a)Sol A is negatively charged and Sol B is positively charged
(b)Both the sols are negatively charged.
(c)Sol A is positively charged and sol B is negatively charged
(d)Both the sols are positively charged.
Answer
Answer (as printed): C
Explanation
If the charge on the cation is high then its flocculation value will be low for an anionic sol, and if the charge on the anion is high then its flocculation value will be low for a cationic sol.As $\mathrm{K_2SO_4}$ has a lower flocculation value than KBr (since $\mathrm{SO_4^{2-}}$ has a higher charge than $\mathrm{Br^{-}}$), sol A is cationic in nature (positively charged).For sol B, $\mathrm{CaCl_2}$ has a lower flocculation value than NaCl due to the higher charge on the calcium ion than the sodium ion. So sol B is negatively charged.