Preparation of a 5.00% Aqueous Potassium Iodide (KI) Solution

Knowledge of how to prepare solutions of specific concentrations, such as a 5.00% aqueous potassium iodide (KI) solution by mass, is crucial in many scientific fields. This article will guide you through the step-by-step process of preparing a 72.5 grams of such a solution, ensuring the accuracy and consistency of your preparation.

Step 1: Calculating the Mass of KI Needed

The first step in preparing the solution involves calculating the mass of potassium iodide (KI) required. This is done by multiplying the total mass of the solution by the percentage of KI by mass.

Mathematically, this can be represented as:

Mass of KI Total mass of solution times; Percentage of KI by mass

Given that the total mass of the solution is 72.5 grams and the desired concentration is 5.00% by mass:

Mass of KI 72.5g times; 0.05 3.625g

Step 2: Determining the Mass of Water Needed

The next step is to calculate the mass of water required. This is achieved by subtracting the mass of KI from the total mass of the solution.

Mathematically, this can be represented as:

Mass of water Total mass of solution - Mass of KI

Using the values from Step 1:

Mass of water 72.5g - 3.625g 68.875g

Step 3: Dissolving KI in Water

The final step is to dissolve the calculated mass of KI in the required mass of water. To achieve this, measure 3.625 grams of KI and dissolve it in 68.875 grams (or 68.9 mL) of distilled water.

Note: Given the solubility of KI (140-148 grams per 100 grams of water at 20°C), 68.9 grams of water will be sufficient to dissolve the 3.625 grams of KI.

Summary and Conclusion

To summarize, the preparation of a 5.00% aqueous potassium iodide solution by mass involves the following steps:

Calculate the mass of KI needed: 72.5g times; 0.05 3.625g Determine the mass of water needed: 72.5g - 3.625g 68.875g (or 68.9 mL) Dissolve 3.625g of KI in 68.875g of water (distilled or deionized water).

The volume of the solution will be negligibly different to 68.9 mL, making this a practical and efficient method for preparing a 5.00% by mass KI solution.

Understanding and following these steps ensures the purity and accuracy of your experimental work. Remember, the key to accurate chemical solutions lies in meticulous preparation and precise measurements.