The sol given below with negatively charged colloidal particles is :

Question

The half-life of $^{65}$Zn is 245 days. After $x$ days, 75% of the original activity remained. The value of $x$ in days is __________ (Nearest integer).}
(Given: $\log 3 = 0.4771$ and $\log 2 = 0.3010$)

Answer 1

To determine which option results in a colloidal solution with negatively charged particles, let's consider each option individually:

KI added to AgNO₃ solution:
When potassium iodide ($ \text{KI} $) is added to a silver nitrate ($ \text{AgNO}_3 $) solution, $ \text{AgI} $, an insoluble ionic compound, forms. The reaction can be represented as: \text{Ag}^+ + \text{I}^- \rightarrow \text{AgI(s)} In this case, the $ \text{AgI} $ colloid tends to adsorb $ \text{I}^- $ ions from the medium, forming a positively charged colloid, so this option does not result in negatively charged colloidal particles.
AgNO₃ added to KI solution (Correct Answer):
When silver nitrate ($ \text{AgNO}_3 $) is added to a potassium iodide ($ \text{KI} $) solution, $ \text{AgI} $ is also formed. In this case, the $ \text{AgI} $ particles adsorb excess $ \text{I}^- $ ions from the solution, leading to the formation of a negatively charged colloid. This is due to the presence of excess iodide ions $ \text{I}^- $ from the solution that are adsorbed on the surface of $ \text{AgI} $, giving the colloidal particles a negative charge.
FeCl₃ added to hot water:
When ferric chloride ($ \text{FeCl}_3 $) is added to hot water, a colloidal solution of ferric hydroxide ($ \text{Fe(OH)_3} $) is formed, which is positively charged due to the adsorption of $ \text{Fe}^{3+} $ ions. Therefore, this option does not result in negatively charged colloidal particles.
Al₂O₃.xH₂O in water:
Hydrated aluminum oxide typically forms a positively charged sol due to the adsorption of $\text{Al}^{3+}$ ions. Thus, this option does not form a negatively charged colloid.

Based on the reactions and the nature of ion adsorption, AgNO₃ added to KI solution is indeed the correct choice, as it forms a negatively charged colloid by adsorbing iodide ions.

Answer 2

To determine which option results in a colloidal solution with negatively charged particles, let's consider each option individually:

KI added to AgNO₃ solution:
When potassium iodide ($ \text{KI} $) is added to a silver nitrate ($ \text{AgNO}_3 $) solution, $ \text{AgI} $, an insoluble ionic compound, forms. The reaction can be represented as: \text{Ag}^+ + \text{I}^- \rightarrow \text{AgI(s)} In this case, the $ \text{AgI} $ colloid tends to adsorb $ \text{I}^- $ ions from the medium, forming a positively charged colloid, so this option does not result in negatively charged colloidal particles.
AgNO₃ added to KI solution (Correct Answer):
When silver nitrate ($ \text{AgNO}_3 $) is added to a potassium iodide ($ \text{KI} $) solution, $ \text{AgI} $ is also formed. In this case, the $ \text{AgI} $ particles adsorb excess $ \text{I}^- $ ions from the solution, leading to the formation of a negatively charged colloid. This is due to the presence of excess iodide ions $ \text{I}^- $ from the solution that are adsorbed on the surface of $ \text{AgI} $, giving the colloidal particles a negative charge.
FeCl₃ added to hot water:
When ferric chloride ($ \text{FeCl}_3 $) is added to hot water, a colloidal solution of ferric hydroxide ($ \text{Fe(OH)_3} $) is formed, which is positively charged due to the adsorption of $ \text{Fe}^{3+} $ ions. Therefore, this option does not result in negatively charged colloidal particles.
Al₂O₃.xH₂O in water:
Hydrated aluminum oxide typically forms a positively charged sol due to the adsorption of $\text{Al}^{3+}$ ions. Thus, this option does not form a negatively charged colloid.

Based on the reactions and the nature of ion adsorption, AgNO₃ added to KI solution is indeed the correct choice, as it forms a negatively charged colloid by adsorbing iodide ions.

The sol given below with negatively charged colloidal particles is :

Show Hint

The Correct Option is B

Solution and Explanation

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