Absolutely, let's dive into the step-by-step process required to prepare a 250 ml solution of oxalic acid with a concentration of 0.2 mol/dm³.
### Step-by-Step Solution:
1. Determine the Number of Moles Required:
- We start by calculating the number of moles of oxalic acid needed for the desired concentration.
- The formula to use is:
[tex]\[
\text{Moles of solute} = \text{Molarity} \times \text{Volume (in liters)}
\][/tex]
- Given:
[tex]\[
\text{Molarity} = 0.2 \ \text{mol/dm}^3, \ \text{Volume} = 0.25 \ \text{liters}
\][/tex]
- Calculation:
[tex]\[
\text{Moles of oxalic acid} = 0.2 \times 0.25 = 0.05 \ \text{moles}
\][/tex]
2. Calculate the Mass of Oxalic Acid Required:
- Next, convert the moles of oxalic acid into grams using the molar mass of oxalic acid dihydrate (H₂C₂O₄·2H₂O).
- The formula to use is:
[tex]\[
\text{Mass} = \text{Moles} \times \text{Molar Mass}
\][/tex]
- Given the molar mass:
[tex]\[
\text{Molar Mass} = 90.03 \ \text{g/mol}
\][/tex]
- Calculation:
[tex]\[
\text{Mass of oxalic acid} = 0.05 \ \text{moles} \times 90.03 \ \text{g/mol} = 4.5015 \ \text{grams}
\][/tex]
3. Describe the Preparation Procedure:
- Step 1: Weigh out 4.5015 grams of pure oxalic acid dihydrate using an accurate balance.
- Step 2: Place the weighed oxalic acid into a beaker.
- Step 3: Add a small amount of distilled water to the beaker to dissolve the oxalic acid completely. Stir the solution with a glass rod until all the solid has dissolved.
- Step 4: Transfer the dissolved solution into a 250 ml volumetric flask.
- Step 5: Rinse the beaker several times with distilled water to ensure all of the oxalic acid has been transferred into the volumetric flask. Add the rinsings to the flask.
- Step 6: Carefully add distilled water to the volumetric flask until the bottom of the meniscus touches the 250 ml mark on the flask.
- Step 7: Stopper the flask and mix the solution thoroughly by inverting it multiple times to ensure a uniform concentration throughout the solution.
By following these steps meticulously, you will prepare a 250 ml solution of oxalic acid with a concentration of 0.2 mol/dm³.
