# Quick Question about theory in solving Ksp?

• RoboNerd
In summary, the conversation discusses the calculation of the equilibrium concentration of Pb+2 ions remaining in a solution after mixing two solutions containing Pb(C2H3O2) and K2CrO4. The percentage of Pb+2 remaining in solution after precipitation is also discussed, with the Ksp for PbCrO4 provided. There is a question about whether it is necessary to use the ICE chart method to solve this problem, or if it is acceptable to simply plug in the values and solve. Both methods give the same numerical answer, but it is uncertain which approach is considered more legitimate.
RoboNerd

## Homework Statement

[/B]
Lead chromate, PbCrO4, is a yellow pigment used in paints. Suppose 0.50 L of a 1.0 x 10-5 M Pb(C2H3O2) and 0.50 L of a 1.0 x 10-3 M K2CrO4 solution are mixed. Calculate the equilibrium concentration of Pb+2 ion remaining in the solution after PbCrO4 precipitates. What is the percentage of Pb+2 remaining in solution after the precipitation has occurred. (The Ksp for PbCrO4 is 1.8 x 10-14)I have a little question regarding theory about how a website solved this problem.

## Homework Equations

The solution is here on page 21 of the document.
http://faculty.icc.edu/bcook/chem132NT/acid_base_eq.pdf

## The Attempt at a Solution

My question is this: is it really necessary to assume initially that this is a limiting reagent problem and have the reaction of Pb2+ and CrO42- go to completion to form the salt and then do the ICE chart calculation for the solubility, or is it OK if I just go and do the ice chart straight away?

I tried both methods, and both gave the same numerical answer, but which approach is more "legit"?

"ICE?" If you have to use it to satisfy "OC" types, do so. Otherwise, plug it in and grind it out.

## 1. What is Ksp and how is it related to solubility?

Ksp, or the solubility product constant, is a measure of the maximum amount of a solute that can dissolve in a solvent at a given temperature. It is related to solubility because it represents the equilibrium between the dissolved and undissolved form of a compound in a solution.

## 2. How do I calculate the Ksp value for a given compound?

To calculate the Ksp value, you need to know the concentrations of the dissolved ions in a saturated solution, and then use those values to solve for the equilibrium constant using the chemical equation for the dissolution of the compound.

## 3. Can the Ksp value change with temperature?

Yes, the Ksp value is dependent on temperature. As temperature increases, the solubility of a compound may also increase, resulting in a higher Ksp value. However, this is not always the case and can vary depending on the compound.

## 4. How does the Ksp value relate to the common ion effect?

The common ion effect states that the solubility of a compound decreases when a common ion is added to the solution. This is because the common ion reduces the concentration of the dissolved ions, shifting the equilibrium towards the undissolved form of the compound. The Ksp value takes into account the concentration of the dissolved ions, so the addition of a common ion will lower the Ksp value.

## 5. Can I use the Ksp value to predict the solubility of a compound?

Yes, the Ksp value can be used to predict the solubility of a compound in a given solvent. If the concentration of the dissolved ions in a solution is equal to or greater than the Ksp value, the solution is considered saturated and the compound is at its maximum solubility. If the concentration is lower than the Ksp value, the solution is unsaturated and more of the compound can dissolve.

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