Kelarutan dan Hasilkali Kelarutan ( Latihan Soal ) - Kimia

Introduction

This tutorial guides you through solving a solubility product constant (Ksp) problem in chemistry, specifically focusing on calcium hydroxide (Ca(OH)2). Understanding Ksp is essential for chemistry students, especially those in high school, as it helps in predicting the solubility of ionic compounds in water.

Step 1: Understand the Problem

Begin by identifying the given data from the problem:

• The solubility of Ca(OH)2 is given as (1 \times 10^{-2}) M.

Next, recognize that Ksp represents the product of the concentrations of the ions in a saturated solution of the compound. For Ca(OH)2, it dissociates in water as follows:

[ \text{Ca(OH)}_2 (s) \rightleftharpoons \text{Ca}^{2+} (aq) + 2 \text{OH}^- (aq) ]

Step 2: Write the Expression for Ksp

The Ksp expression for the dissociation of Ca(OH)2 can be written as:

[ Ksp = [\text{Ca}^{2+}][\text{OH}^-]^2 ]

Where:

• ([\text{Ca}^{2+}]) is the concentration of calcium ions.
• ([\text{OH}^-]) is the concentration of hydroxide ions.

Step 3: Determine Ion Concentrations

From the solubility of Ca(OH)2:

• The concentration of ([\text{Ca}^{2+}]) is equal to the solubility: [ [\text{Ca}^{2+}] = 1 \times 10^{-2} \text{ M} ]
• Since each formula unit of Ca(OH)2 produces two hydroxide ions, the concentration of hydroxide ions is: [ [\text{OH}^-] = 2 \times (1 \times 10^{-2}) = 2 \times 10^{-2} \text{ M} ]

Step 4: Substitute the Values into the Ksp Expression

Now, insert the values into the Ksp expression:

[ Ksp = (1 \times 10^{-2}) \times (2 \times 10^{-2})^2 ]

Step 5: Calculate Ksp

Carry out the calculation step-by-step:

1. Calculate ((2 \times 10^{-2})^2): [ (2 \times 10^{-2})^2 = 4 \times 10^{-4} ]
2. Now multiply by the concentration of ([\text{Ca}^{2+}]): [ Ksp = (1 \times 10^{-2}) \times (4 \times 10^{-4}) = 4 \times 10^{-6} ]

Step 6: Analyze Answer Choices

From the calculation, we find that: [ Ksp \text{ for Ca(OH)}_2 = 4 \times 10^{-6} ] Now, compare this result with the answer choices provided:

• A. (1 \times 10^{-6})
• B. (2 \times 10^{-6})
• C. (4 \times 10^{-6}) (Correct Answer)
• D. (2 \times 10^{-4})
• E. (4 \times 10^{-4})

Conclusion

In this tutorial, we calculated the solubility product constant for calcium hydroxide. The key steps included understanding the dissociation, writing the Ksp expression, determining ion concentrations, and performing the necessary calculations. The correct Ksp value for Ca(OH)2 is (4 \times 10^{-6}).

For further practice, consider applying this method to other ionic compounds and their solubility products to strengthen your understanding.