# Ksp and Q precipitate, Why does volume of water matter

• AMan24
In summary, the person is asking why they need to add 40 liters of water to the volume of AgCl when it is not going to dissolve. They state that this is because the reaction may form a precipitate, even if it is not soluble in water. They also state that the final equilibrium does not depend on the path followed to get to the final state.
AMan24

## The Attempt at a Solution

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So here's my question again, why do you need to include 40L of water in the total volume? It's not like AgCl is going to dissolve in water right? AgCl has low solubility in water. I mean if it was like NaCl then you should include the water because it dissolved, but if it was something that isn't soluble in water at all, then why would you include the water?

Lets say you did a reaction like this and it formed something that isn't solube in water at all, if you include the water in the math, the math will say no precipitate formed, but in reality there will be a precipitate formed.

So for this reaction i'd say a precipitate will form but a small part of it would be dissolved

It is Q that defines what will precipitate and what will not. To calculate Q you need concentrations. How are you going to calculate concentrations without taking the final volume into account?

Does it have anything to do with water being added in the beginning? So a precipitate never forms in the first place because the concentrations are too low, if it is then i guess i kind of understand it

Why would the situation be different if the water was added later? Why do you think AgCl would not dissolve? It may have low solubility, but it still follows Ksp. Plus, the final equilibrium doesn't depend on the path followed to get to the final state. It sometimes does, when reactions are irreversible, but that's not the case here.

what is Ksp of AgCl ?
it is the ionic product of [Ag+ ] and [Cl-] .These are the concentration of ions in solution and solution means solute (AgCl) and solvent( water here).It is not that AgCl is completely insoluble, its very low Ksp indicates that it is very less soluble.It means volume of water added do matter in precipitation of AgCl and cases will be there where Q<Ksp just because of excess water...like in your problem.

## 1. What is Ksp and Q precipitate?

Ksp (solubility product constant) is a measure of the maximum amount of a solute that can dissolve in a solvent at a given temperature. Q precipitate is the calculated ion product, which is compared to Ksp to determine if a precipitate will form.

## 2. How is Ksp and Q precipitate calculated?

Ksp is calculated by multiplying the concentrations of the ions in a saturated solution at equilibrium. Q precipitate is calculated by multiplying the concentrations of the ions in a given solution at any point in time.

## 3. Why does the volume of water matter in Ksp and Q precipitate?

The volume of water plays a crucial role in determining the solubility of a substance. A larger volume of water can dissolve more solute, increasing the concentration of ions and potentially altering the Ksp and Q precipitate values.

## 4. How does temperature affect Ksp and Q precipitate?

Temperature has a significant impact on the solubility of a substance and therefore on Ksp and Q precipitate values. In general, an increase in temperature leads to an increase in solubility and vice versa.

## 5. Can Ksp and Q precipitate be used to predict the formation of a precipitate?

Yes, Ksp and Q precipitate values can be used to predict the formation of a precipitate. If Q precipitate is greater than Ksp, a precipitate will form, and if Q precipitate is less than Ksp, no precipitate will form.

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