A sol of $AgI$ is prepared by mixing equal
volumes of $0.1M \, AgNO_3$ and $0.2M KI$, which of
the following statement is correct ?
- Sol obtained is a negative sol with $NO^-_3$ adsorbed on $AgI$
- Sol obtained is a positive sol with $Ag^+$ adsorbed on $AgI$
- Sol obtained is a positive sol with $K^+$ adsorbed on $AgI$
- Sol obtained is a negative sol with $I^-$ adsorbed on $AgI$
The Correct Option is D
Approach Solution - 1
Given reaction is, \(AgNO _{3}+ KI \rightarrow Agl ( Sol )+ KNO _{3}\)
Here, the amount of \(AgNO _{3}\) present is \(0.1 \,M\). Amount of \(KI\) present is \(0.2\, M\).
Since \(KI\) is excess here, thus, sol obtained is a negative sol with \(I\) adsorbed on \(AgI\).
Approach Solution -2
When equal volumes of 0.1 M AgNO\(_3\) and 0.2 M KI are mixed, Ag\(^+\) ions from AgNO\(_3\) react with I\(^-\) ions from KI to form AgI, which precipitates out initially. However, the precipitation reaction can lead to the formation of a sol of AgI.
In this case, the AgI particles formed will carry a positive charge because of the excess K\(^+\) ions that remain in the solution and adsorb on the surface of the AgI particles. This adsorption of K\(^+\) ions imparts a positive charge to the sol. Hence, the sol obtained is a positive sol with K\(^+\) adsorbed on AgI.
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Concepts Used:
Colligative Properties
Colligative Property of any substance is entirely dependent on the ratio of the number of solute particles to the total number of solvent particles but does not depend on the nature of particles. There are four colligative properties: vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure.
Examples of Colligative Properties
We can notice the colligative properties of arrangements by going through the accompanying examples:
- On the off chance that we add a spot of salt to a glass full of water, its freezing temperature is brought down impressively than its normal temperature. On the other hand, the boiling temperature is likewise increased and the arrangement will have a lower vapor pressure. There are also changes observed in its osmotic pressure.
- In the same way, if we add alcohol to water, the solution’s freezing point goes down below the normal temperature that is usually observed for either pure alcohol or water.
Types of Colligative Properties
- Freezing point depression: ΔTf =1000 x kf x m2 /(M2 x m1)
- Boiling point elevation: ΔTb = kb m
- Osmotic pressure: π = (n2/V) RT
- Relative lowering of vapor pressure: (Po - Ps)/Po