Using your 0.0100M oxalate solution and only the equipment and supplies listed below, describe how to prepare a 0.00025M solution of oxalate. Note, you are not allowed to add volumes with pipettes. (example, if you want 20mLs, you can not use a 10mL + 10mL addition as this adds error). Using the dilution formula, prove that your method will lead to the proper molarity.
1mL, 2mL, 10mL, 20mL, 25mL pipettes
100mL or 250mL volumetric flask
Water
I suggest you first do the dilution of the stock solution by a x10 in order to get 0.001M solution.
1. Pipette out 25mL of the stock solution into a 250mL v.flask, top up with water to the mark.
2. Top up to the mark with water using wash bottle or dropper.
Your new solution should now be in the 250mL v.flask with a 0.001M label. Now, the desired solution is 0.00025M. So M1v1 = M2v2 for dilution method;
M1 = 0.001M (the molarity of the solution you prepare, NOT the stock solution)
v1 = ??? (we need to know the exact amount of volume to extract from the 0.001M solution)
M2 = 0.00025M (the desired molarity to prepare).
v2 = 100mL (we can use a 100mL v.flask as it is suitable to use to make a 0.00025M).
rearranging for v1 gives;
v1 = (0.00025x0.100)/0.001 = 25mL
i.e. pipette out 25mL from the 0.001M solution you prepared into a 100mL v.flask, top up with water to the mark.
To prepare a 0.00025M solution of oxalate using the given equipment and supplies, follow the steps below:
1. Start by calculating the volume of the 0.0100M oxalate solution needed for the dilution. You can use the dilution formula, which is defined as M1V1 = M2V2, where M1 is the initial molarity, V1 is the initial volume, M2 is the final molarity, and V2 is the final volume.
Let's assume you want to prepare a 100mL solution of oxalate.
Rearranging the formula, we have V1 = (M2 x V2) / M1.
Substituting the values, V1 = (0.00025M x 100mL) / 0.0100M.
After calculating, we find V1 = 2.5mL. Therefore, you will need 2.5mL of the 0.0100M oxalate solution.
2. Take the 100mL volumetric flask and add 2.5mL of the 0.0100M oxalate solution using a pipette. This will ensure the correct concentration of the solute in the final solution.
3. Then, fill the volumetric flask with water. Use a wash bottle to add water until the solution reaches the 100mL mark on the volumetric flask.
4. Carefully mix the solution by inverting the flask a few times to ensure proper mixing.
By following these steps, you have prepared a 0.00025M solution of oxalate.
To verify that the method leads to the correct molarity, you can use the dilution formula again:
M1V1 = M2V2
0.0100M x 2.5mL = 0.00025M x 100mL
0.025 = 0.025
Since both sides of the equation are equal, this demonstrates that the method leads to the proper molarity of 0.00025M.