Would it be better to use an unknown acid sample of a size that should require 10ml or one that requires 15ml of the titrant

Answer 1

I would use the larger volume. Why? Because the buret can be read to 0.02 mL no matter what the volume is but 0.02 mL out of 10mL is a larger percent error than 0.02 mL our of 15 mL.