# Calculating the Ksp of Calcium hydroxide at room temp

• Zoey Brown
In summary: The CO2 would have reacted with the OH- from the water to produce CO2 and H2O. The H2O would have made the Ca(OH)2 more basic, and the more basic Ca(OH)2 would have reacted with the KHP more than the less basic KHP.
Zoey Brown

## Homework Statement

I conducted a titration experiment in which 0.1g of KHP was dissolved in 50mL of distilled water and placed in an Erlenmeyer flask. I filtered a Ca(OH)2 solution (that was left out open on the lab benches for us to use) and put that into the burette and titrated. Ultimately, the Ksp i calculated was 3.0 x10^-7 whereas the accepted Ksp value is 5.02 x10^-6. This gave me a percent error of 94%. I'm not as concerned about the fact that i got a huge error as much as i don't understand why. Some of the possible errors i can think of are that the temperature was cooler than 25 degrees and that the solution wasnt filtered properly. The issue is that both of those errors would have caused higher Ksp values than the accepted, not lower like mine.

## Homework Equations

c=n/V
Ksp= [Ca 2+][OH -]^2

## The Attempt at a Solution

I know that if my Ksp is lower, my concentrations must be lower which means i used too much calcium hydroxide. i don't know why however

How precisely was the KHP weighted? Was it correctly dried before use? What indicator was used?

the KHP was measured exactly each trial, all proper titration procedures were followed, and phenolphthalein was used. However, in any case i doubt such errors would result in such a large deviation from the theoretical value

Separately not, but they could combine producing a larger error than expected.

If the solution was left in the open it was partially neutralized by CO2 before you started the titration.

So if the solution was partially neutralized by carbon dioxide, would that mean that it was less basic and therefore more of the calcium hydroxide solution would have to be used in order for it to be standardized by the KHP? And that would be a cause for the increase in volume used, which decreases concentration, and creates a lowe Ksp than the theoretical value?

Yes.

## 1. How do you calculate the Ksp of calcium hydroxide at room temperature?

To calculate the Ksp of calcium hydroxide at room temperature, you will need the solubility product constant (Ksp) value, which can be found in a reference book or online. Then, you will need to measure the concentration of calcium ions and hydroxide ions in a saturated solution of calcium hydroxide at room temperature. Finally, use the formula Ksp = [Ca2+][OH-]^2 to calculate the Ksp value.

## 2. What is the solubility product constant (Ksp) of calcium hydroxide at room temperature?

The solubility product constant (Ksp) of calcium hydroxide at room temperature is approximately 5.5 x 10^-6 at 25°C. However, this value may vary slightly depending on the source and purity of the calcium hydroxide.

## 3. How does temperature affect the Ksp of calcium hydroxide?

An increase in temperature generally leads to an increase in the solubility of calcium hydroxide, which results in a higher Ksp value. This is because higher temperatures provide more energy for the solute particles to break apart and dissolve in the solvent. However, other factors such as pressure and the presence of other substances in the solution can also affect the Ksp of calcium hydroxide at different temperatures.

## 4. What are the units for the Ksp of calcium hydroxide?

The units for the Ksp of calcium hydroxide are mol^2/L^2. This reflects the fact that the Ksp value is calculated by multiplying the concentration of calcium ions [Ca2+] by the concentration of hydroxide ions [OH-]^2.

## 5. How accurate are Ksp values for calcium hydroxide at room temperature?

The accuracy of Ksp values for calcium hydroxide at room temperature may vary depending on the source and method of measurement. Generally, these values are accurate enough for most practical applications and scientific experiments. However, it is important to note that slight variations may occur due to different experimental conditions or sources of calcium hydroxide. Therefore, it is always recommended to double-check the accuracy of Ksp values before using them in calculations or experiments.

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