Surface Chemistry - Result Question 20

####21. The coagulating power of electrolytes having ions $Na^{+}, Al^{3+}$ and $Ba^{2+}$ for arsenic sulphide sol increases in the order

(a) $Al^{3+}<Ba^{2+}<Na^{+}$

(b) $Na^{+}<Ba^{2+}<Al^{3+}$

(c) $Ba^{2+}<Na^{2+}<Al^{3+}$

(d) $Al^{3+}<Na^{+}<Ba^{2+}$

(2013 Main)

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Answer:

Correct Answer: 21. (d)

Solution:

  1. According to Hardy Schulze rule, greater the charge on oppositely charged ion, greater is its coagulating power. Since arsenic sulphide is a negatively charged sol, thus, the order of coagulating power is $Na^{+}<Ba^{2+}<Al^{3+}$.


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