Question

suppose your unknown brass sample consists of a piece of hardware, such as a screw, and your lab is tasked with determining the copper content of the sample. One screw is not large enough to give a sufficiently concentrated solution of copper(II) ion when dissolved and diluted to 250 mL. Would you dissolve one piece or two pieces and why?

Answer 1

Let's discuss the pros and cons of both the cases:-

If you dissolve one piece of screw than you would get the sufficiently concentrated solution but you will have to go with the assumption that both the screws were of exact same composition and contained same amount of copper, which is practically not possible.

But if the experiment forbids this assumption than you can use only one screw for carrying out the experiment provided that you diluted the solution to 125 ml only otherwise you will not get sufficiently concentrated solution. But in this method you will get less solution and you may not be able to take enough observations.

So, it completely depends on you and your experimental requirements that in which way you are willing to compromise.