Question

Assertion :In the coagulation of a negative sol the flocculating power is in the order :
$A{l}^{3+}$>$B{a}^{2+}$>$N{a}^{+}$ Reason: Greater the valence of the flocculating ion added, greater is its power to cause precipitation.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

• When an excess of an electrolyte is added, the colloidal particles are precipitated. The reason is that colloids interact with ions carrying a charge opposite to that present on themselves. This causes neutralization leading to their coagulation.
• The ion responsible for neutralization of charge on the particles is called the coagulating ion. A negative ion causes the precipitation of positively charged sol and vice versa.
  
• The greater the valence of the flocculating ion added, the greater is its power to cause precipitation. This is known as a Hardy-Schulze rule.
  
• Here, the order of valence is $A{l}^{3+}>B{a}^{2+}>N{a}^{+}$ and hence the order of flocculating power.
• Hence, both assertion and reason are correct and also reason is the correct explanation for the assertion.