Question

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

Answer 1

What about 25 mL of 0.01M and dilute to 100. You now have
0.01M x (25/100) = 0.0025.
Now dilute that by 10; 10 mL of that to 100.
0.0025M x (10/100) = 0.00025M

Note: The problem doesn't say that you have TWO 100 mL volumetric flasks; if you have only one 100 mL volumetric flask that would mean you had to pipet 10 mL from the first dilution, clean the flask and use it the second time for the second 10 fold dilution

If that isn't allowed you could make the second 10 fold dilution by using the 25 mL pipet and diluting to 250 mL. (That means using the 25 mL pipet a second time, too, and I don't know if that is allowed).